Bunuel wrote:
The company's chief executive, whose technological expertise, views on the future of the industry, and decision-making style were impressive to the managers who worked with her, was also acknowledged as a leading strategist by many people outside her firm, including executives at rival companies, whose approaches often differed substantially from her own.
(A) were impressive to the managers who worked with her, was also acknowledged as a leading strategist by many people outside her firm, including executives at rival companies, whose approaches often differed substantially from
(B) impressed the managers who worked with her, also was acknowledged as a leading strategist by many people outside her firm, including executives at rival companies, whose approaches often differed substantially from
(C) was impressive to the managers who worked with her, was also acknowledged as a leading strategist by many people outside her firm, that included executives at rival companies, whose approaches were different substantially in comparison to
(D) was impressive to the managers who worked with her, also acknowledged as a leading strategist by many people outside her firm, who included executives at rival companies, the approaches of whom differed substantially when compared to
(E) were an impression to the managers who worked with her, also was acknowledged as a leading strategist by many people outside her firm, including executives at rival companies, whose approaches were often substantially different from that of
OFFICIAL EXPLANATION
B
The first word of the underlined portion should not be singular, since it refers to all three items in the preceding list. Thus, (C) and (D) can be eliminated. The phrase "were an impression", which opens (E), is extremely unidiomatic, so (E) can eliminated as well.
If you focus only on the beginning of the underlined portion, (B) is preferable to (A), as (B) does not employ the passive voice. This is a subtle distinction, but the sort of thing that makes one answer superior to another on a di¢ cult question. Also, "also was acknowledged" is preferable to "was also acknowledged", since there was no previous "was" in the sentence, and "also was acknowledged" put the entire verb ("was acknowledged") in one place. Choice (B) is correct.