Official Explanation

The argument concludes that rising sea levels caused by global warming will destroy major coastal population centers and displace millions of people. Any assumption in support of this conclusion would have to corroborate that these events will definitively take place.

(A) CORRECT. If new technological developments in the next century allow people to divert rising seas from the world’s cities (i.e., population centers), cities will not be destroyed and millions of people will not be displaced. Thus, a necessary assumption is that these technologies will not be developed.

(B) A simple awareness of the steps to reduce emissions in no way undermines the argument’s conclusion, as this answer choice does not describe any action being taken by individuals. Additionally, greenhouse gases are never mentioned as the primary by-product of human activity that causes global warming, and are therefore not sufficient to address the argument.

(C) The argument never suggests that all coastal population centers are similarly affected; this choice is too extreme and overreaching for the argument’s conclusion.

(D) This might be true, but it is not an assumption on which the conclusion rests. Instead, this answer choice is simply an inference that might be drawn from the premises.

(E) The idea that human activity is the sole cause of global warming is neither suggested nor assumed by the argument. In addition, the wording "sole cause" is too extreme.

Answer: A