Question 30

(E) The beginning of the sentence cries out for a verb where the underlined segment begins. Simplified, the sentence states "Only among [certain] populations do people retain [something] . . . ."

(A) The "only . . . do people retain" structure is missing. It is verbose and unidiomatic to say "the ability that they can produce. The ability to produce" says it clearly and succinctly.

(B) The correct "only . . . do" structure is missing, although "the ability to produce" is idiomatic.

(C) The verb "is" rings true structurally, but one needs to read the rest of the statement to sense how verbose and awkward it is in comparison with version E. "The ability" and its completing "to produce" are separated by a number of words. "The ability to reproduce" should not be pulled apart.

(D) The phrase "the ability for producing" is unidiomatic. "The ability to reproduce" is correct.