"Surprising" Phenomenon
Why do smokers who smoke one pack a day have identical levels of nicotine in their blod at the end of the day regardless of whether they smoke a pack of high-nicotine cigarettes or low-nicotine cigarettes?
Objective
The correct answer should give us a reason that the difference between high-nicotine packs and low-nicotine packs might not lead to a difference in nicotine levels in blood at the end of the day for smokers who smoke one pack.
A
Blood cannot absorb more nicotine per day than that found in the smoke from a package of the lowest-nicotine cigarettes available.
This establishes a ceiling for nicotine in one’s blood and that low-nicotine packs already lead to nicotine levels at that ceiling. High-nicotine packs have more nicotine, but won’t go above the ceiling of nicotine levels in people’s blood.
B
Smokers of the lowest-nicotine cigarettes available generally smoke more cigarettes per day than smokers of high-nicotine cigarettes.
The statistic in the stimulus involves smokers who smoke just one pack a day. This controls for varying amounts of cigarettes.
C
Most nicotine is absorbed into the blood of a smoker even if it is delivered in smaller quantities.
Even if this is true, if low-nicotine packs have less nicotine overall, we would still expect less nicotine in their blood.
D
The level of tar in cigarettes is higher in low-nicotine cigarettes than it is in some high-nicotine cigarettes.
We have no reason to suspect the level of tar in cigarettes impacts the level of nicotine in one’s blood.
E
When taking in nicotine by smoking cigarettes is discontinued, the level of nicotine in the blood decreases steadily.
We’re concerned about nicotine levels after smoking. What happens to nicotine when people stop smoking doesn’t help explain the identical nicotine levels observed after smoking.
Summarize Argument: Phenomenon-Hypothesis
The author concludes that testosterone tends to promote heart disease, and estrogen tends to inhibit heart disease. This is based on the following:
Heart disease generally affects men earlier than it does women. Women tend to experience heart disease after menopause.
When men and women are young, men have ten times more testosterone than women.
Women lose estrogen after menopause.
Identify and Describe Flaw
The author assumes that a correlation between higher testosterone and increased heart attacks is explained by testerone’s causing heart attacks. The author also assumes that women’s decreased risk of heart attack compared to men when young is expained by estrogen helping to prevent heart attacks.
A
Hormones are the primary factors that account for the differences in age-related heart disease risks between women and men.
The author doesn’t assume that hormones are the “primary” factors. He does assume that hormones are at least one factor, but that doesn’t mean he thinks they are the most important factor.
B
Estrogen and testosterone are the only hormones that promote or inhibit heart disease.
The author doesn’t assume these are the only hormones that affect heart disease risk. He does assume that these hormones affect the risk, but that doesn’t mean he thinks other hormones have no effect.
C
Men with high testosterone levels have a greater risk for heart disease than do postmenopausal women.
The author never compares the risk of heart disease between men with high testosterone levels and women after menopause.
D
Because hormone levels are correlated with heart disease they influence heart disease.
The author assumes that correlation between testerone levels and increased heart attacks, as well as between estrogen and decreased heart attacks, implies a causal relationship between those hormones and heart disease.
E
Hormone levels do not vary from person to person, especially among those of the same age and gender.
The author does not assume that every single person of the same age and gender has the exact same hormone levels. If there are variations from person to person, that doesn’t undermine the author’s reasoning, which is based on general correlations.
Summarize Argument
The author concludes that a disease that would have had minor impacts on food supply in the past would be devastating today. This prediction is based on the observation that today’s crops lack diversity compared to crops in the past because farmers today only plant a few strains of a given crop.
Notable Assumptions
The author assumes that farmers today don’t have any way besides diversity to protect against diseases.
A
In the past, crop diseases would often devastate food supplies throughout entire regions.
The conclusion discusses specifically the diseases that would have had only minor impacts on the food supply in the past; the diseases referenced in (A) are outside of the scope of the argument.
B
Affected crops can quickly be replaced from seed banks that store many strains of those crops.
This weakens the argument. It gives a reason that a disease that would have had a minor impact on the food supply in the past would not be devastating today: today’s farmers have another way to protect against the disease other than crop diversity.
C
Some of the less popular seed strains that were used in the past were more resistant to many diseases than are the strains popular today.
This compares the less popular strains of the past with the popular modern strains; this comparison isn’t relevant. (C) also tells us that some old strains were more robust than the popular modern strains, which is consistent with the claim that today’s crops are more vulnerable.
D
Humans today have more variety in their diets than in the past, but still rely heavily on cereal crops like rice and wheat.
The argument is about the crops that make up the food supply, not specifically human diets as a whole, so this is not relevant to the argument.
E
Today’s crops are much less vulnerable to damage from insects or encroachment by weeds than were crops of a few generations ago.
The argument is specifically about the damage caused by diseases; it could be the case that today’s crops are safer from insects and weeds, but that diseases are still able to devastate today’s food supply.