Official Solution:The new mayor is certainly more progressive than her predecessor, but she is not nearly as efficient.A. but she is not nearly as efficient
B. but she, however, is not nearly as efficient
C. but she is nearly not so efficient
D. even though being not as efficient
E. even though her efficiency is not so
A. CORRECT. The conjunction “but” correctly introduces a contrasting independent clause. The second clause is concise, without any redundancy. Note: Use of pronoun “she” is alright - it unambiguously refers to “the new mayor”. If s pronoun is the subject of a clause, by virtue of parallelism, it unambiguously refers to the subject of another clause in the sentence, even though there might be two different subjects that could be possible antecedents. B. The “however” is redundant along with “but”.
C. The adverb “nearly” is misplaced. "Nearly" should refer to “efficient”, not "not" - hence "nearly" should come AFTER "not" as close as possible to “efficient”.
D. The conjunction “though” introduces a dependent clause. In this option it falsely introduces the phrase “being not as efficient” rather than a clause.
E. This option depicts an illogical implication - it compares the new mayor’s efficiency with her predecessor, whereas the new mayor herself must be compared with her predecessor. The construction indicates that the new mayor's efficiency is not as progressive.
Answer: A