A then B then C then D

If A, then B.
If B, then C.
If C, then D.

If all of the statements above are true, which of the following must also be true?

(A) If D, then A.
(B) If not B, then not C.
(C) If not D, then not A.
(D) If D, then E.
(E) If not A, then not D.

Top notch high school graduates

Everyone who has graduated from TopNotch High School has an intelligence quotient (IQ) of over 120. Most students with an IQ of over 120 and all students with an IQ of over 150 who apply to one or more Ivy League universities are accepted to at least one of them.

The statements above, if true, best support which of the following conclusions?

(a) Every graduate of TopNotch High School with an IQ of 150 has been accepted to at least one Ivy-League school.
(b) If a person is a high-school graduate and has an IQ of less than 100, he or she could not have been a student at TopNotch High School.
(c) If a person has an IQ of 130 and is attending an Ivy-League school, it is possible for him or her to have graduated from TopNotch High School.
(d) At least one graduate from TopNotch high school who has applied to at least one Ivy-League university has been accepted to one of them.
(e) If a high-school graduate has an IQ of 150 and is not attending an Ivy-League school, then he or she did not apply to one of them.

Rice Production in Teruvia

In Teruvia, the quantity of rice produced per year is currently just large enough to satisfy domestic demand. Teruvia’s total rice acreage will not be expanded in the foreseeable future, nor will rice yields per acre increase appreciably. Teruvia’s population, however, will be increasing significantly for years to come. Clearly, therefore, Teruvia will soon have to begin importing rice.

Which of the following is an assumption on which the argument depends?

A. No pronounced trend of decreasing per capita demand for rice is imminent in Teruvia.
B. Not all of the acreage in Teruvia currently planted with rice is well suited to the cultivation of rice.
C. None of the strains of rice grown in Teruvia are exceptionally high-yielding.
D. There are no populated regions in Teruvia in which the population will not increase.
E. There are no major crops other than rice for which domestic production and domestic demand are currently in balance in Teruvia.

Air pollution

In 1986, the city of Los Diablos had 20 days on which air pollution reached unhealthful amounts and a smog alert was put into effect. In early 1987, new air pollution control measures were enacted, but the city had smog alerts on 31 days that year and on 39 days the following year. In 1989, however, the number of smog alerts in Los Diablos dropped to sixteen. The main air pollutants in Los Diablos are ozone and carbon monoxide, and since 1986 the levels of both have been monitored by gas spectrography.

Which of the following statements, assuming that each is true, would be LEAST helpful in explaining the air pollution levels in Los Diablos between 1986 and 1989?

• (A) The 1987 air pollution control measures enacted in Los Diablos were put into effect in November of 1988.
• (B) In December of 1988 a new and far more accurate gas spectrometer was invented.
• (C) In February of 1989, the Pollution Control Board of Los Diablos revised the scale used to determine the amount of air pollution considered unhealthful.
• (D) In 1988 the mayor of Los Diablos was found to have accepted large campaign donations from local industries and to have exempted those same industries from air pollution control measures.
• (E) Excess ozone and carbon monoxide require a minimum of two years to break down naturally in the atmosphere above a given area.