Demographic experts predict that the global human population - weaken

Expert's Prediction: the global human population will reach its peak sometime in the middle of this century, after which it will begin to decline

Experts' Proposal: expand educational and economic opportunities to women in developing countries to bring about an earlier and smaller population peak.

We have to weaken the proposal. Something that says that expanding these opportunities will not being about an earlier and smaller peak.

(A) The demographic experts proposing expanding opportunities for women in developing countries made the same recommendations over twenty years ago.

Does not weaken the proposal. The proposal was made before just shows that it makes sense.

(B) The experts' prediction is based on realistic assessments of the educational and economic opportunities that can be made available to women in developing countries before that time.

The prediction is that the peak will be reached in the middle of the century. If this prediction is based on realistic assessment of opportunities that can be made available, it is unlikely that the opportunities can be expanded faster than what has been assumed to make the prediction. Hence, it is unlikely that the proposal of an earlier peak will succeed because it is not realistic. Correct.

(C) Many women in industrialized countries will continue to have four or more children despite access to a variety of educational and economic opportunities.

Number of children is not discussed in the argument. Fewer than before is the aim. This is a given premise - "It is known that when women have access to education and economic opportunities, they choose to have fewer children."

(D) The demographic experts fail to explain why an earlier and smaller population peak is preferable to a later and larger peak.

Irrelevant. Aim is an earlier and smaller peak. Why it is the aim is not relevant to our argument.

(E) Expanding opportunities to women in developing countries is generally considered a positive outcome regardless of its impact on population levels.

Though true, it doesn't weaken our proposal. It just provides all the more reason for the implementation of the proposal.

Answer (B)