Official Solution:
The current floods in Pakistan have been caused by an incessant spell of rains, which, according to the prediction of weather scientists, will continue into late next month and which they consider to be the worst in the area for nearly a century.
A. which, according to the prediction of weather scientists, will continue into late next month and which they consider to be
B. a spell that, according to the prediction of weather scientists, to continue into late next month and is considered
C. a spell that, according to the prediction of weather scientists, will continue into late next month and that they consider
D. a spell, the weather scientists predict, to continue into late next month and they consider
E. which, the weather scientists predict, will continue into late next month and they consider as
A. The idiom “consider X to be Y” is wrong. The correct usage is “consider X Y”.
B. Parallelism is lost for the conjunction “and”. The parts “to continue” (a prepositional phrase / infinitive) and “is considered (a verb)'' are wrongly placed in parallel.
C. CORRECT. The sentence uses an absolute phrase with two relative clauses in parallel:
A spell that…will continue….. and that….they consider…
The idiom “consider X Y” is correct.
D. Parallelism is lost for the conjunction “and”. The parts “to continue” (a prepositional phrase / infinitive) and “consider” (a verb) are wrongly placed in parallel.
It is not clear what they consider the worst in the area. In other words, in the idiom “consider X Y”, X is missing.
E. The idiom “consider X as Y” is wrong. The correct usage is “consider X Y”.
It is not clear what they consider the worst in the area. In other words, in the idiom “consider X Y”, X is missing. Repeating “which” after “and” would make this construction clear. A correct construction could be:
“which… will continue … and which they consider the worst….”
Answer: C