Sharply fewer ducks are expected to migrate south this fall and may be the lowest figure on record, according to United States and Canadian wildlife experts.
A.
Sharply fewer ducks are expected to migrate south this fall and may be - Sharply fewer ducts? if the intention here was to highlight a drop in the expected number of ducks, then this is certainly an awkward way to do so.
If you isolate the second clause that is involved in the parallelism, what we get is: Sharply fewer ducks may be the lowest form... - This does not make any sense at all. Hence,
eliminate (A)B.
It is expected that sharply fewer ducks will migrate south this fall and will perhaps be - If you isolate the parallel clauses, we get:
clause #1: It is expected that sharply fewer ducks will migrate south this fall - here, the adverb 'sharply' is redundant, since the word 'fewer' already signals a drop in the expected number of ducks.
Clause #2: it is expected that sharply fewer ducks will perhaps be the lowest figure on record - how can ducks be compared to a 'figure'? This does not make sense.
hence,
eliminate (B)C.
The ducks expected to migrate south this fall will be sharply reduced, perhaps to - the ducks...will be sharply reduced? A duck population can be reduced but you cannot reduce a duck - that wouldn't make any sense whatsoever. Hence,
eliminate (C).D.
The number of ducks that will migrate south this fall is expected to drop sharply, perhaps to - (D) makes it clear that it is "the number of ducks" that is expected "to drop". Moreover, the phrase ''perhaps to the lowest figure on record'' clearly modifies the "drop". (D) therefore has no error. Hence,
(D) is the right answer choice.
E.
A sharp drop is expected in the number of ducks that will migrate south this fall, which may be - the relative clause ''which may be..." tries to modify the noun 'fall', whereas it is the 'drop (of number of ducks)' that should be modified by this relative clause. Hence,
eliminate (E).