Understanding the argument -
There are far fewer children available for adoption than there are people who want to adopt. - Conclusion.
Two million couples are currently waiting to adopt, but in 1982, the last year for which figures exist, there were only some 50,000 adoptions. - Supporting premise. Mind you, it says "ADOPTIONS" and "number of children." What if 20 million children were available? Then, the conclusion will not hold.
Which of the following statements, if true, most strengthens the author’s claim that there are far fewer children available for adoption than there are people who want to adopt?
(A) The number of couples waiting to adopt has increased significantly in the last decade. - We don't know about the number of children.
(B) The number of adoptions in the current year is greater than the number of adoptions in any preceding year. - The increase in adoptions could be due to an improved adoption process. So, this option doesn't shed any light on the supply/demand aspect.
(C) The number of adoptions in a year is approximately equal to the number of children available for adoption in that period. - Yes. It shows the gravity of the issue, meaning 100% adoption and still a gap of 1.95 million. Ok.
(D) People who seek to adopt children often go through a long process of interviews and investigation by adoption agencies. - out of scope.
(E) People who seek to adopt children generally make very good parents. - out of scope.