Vehicular collisions on the interstate highway have declined steadily during the first four months of this year but virtually remained unchanged during the next five months.
(A) have declined steadily during the first four months of this year but virtually remained unchanged
“during the first four months of this year” implies that the decline happened in tha past, and hence present perfect doesn’t make sense.
The next action “remained unchanged” took place later. So, it doesn’t make sense if the earlier action is in present perfect while the later action is in past. Past comes before present perfect.
(B) declined steadily during the first four months of this year but virtually remain unchanged
“remain unchanged” is in present tense and thus doesn’t make sense with “next five month” which is past.
(C) steadily declined during the first four months of this year but remain virtually unchanged
“remain unchanged” is in present tense and thus doesn’t make sense with “next five month” which is past.
(D) declined steadily during the first four months of this year but have remained virtually unchanging
“have remained unchanging” is not a viable construction.
(E) declined steadily during the first four months of this year but have remained virtually unchanged
Correct sequence of tenses and correct usage of constructions.
Hence E