The insurance behemoth has announced that it will hire 1,200

Choice A has a misplaced modifier, because which must grammatically modify Europe. The logic of the sentence is that the actions described in the first clause, not Europe itself, are part of an effort. The possessive adjective their is plural, so it doesn't agree with its noun, insurance behemoth. (See its field at the end of the sentence.)

Choice B: [A]n effort to try is redundant. The word effort already conveys the idea of "trying". The article a in front of part is clumsy and unnecessary, but probably not reason enough on its own to eliminate.

Choice C: Here the phrase an effort solidifying contradicts itself. It is just an effort, but solidifying implies that the goal has been achieved! The idiomatic expression is "an effort to" followed by the infinitive. As in choice B, the article a before part is clumsy.

Choice D. Here we have the same error in pronoun agreement seen in choice A. The possessive adjective their is plural but refers to the singular noun insurance behemoth. The article a before part is clumsy.

Choice E. This choice omits the awkward article a before part. The proper idiom after effort, "effort to" + infinitive, is used. This choice also uses the correct possessive adjective its referring to insurance behemoth.

Terry Serres
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The Princeton Review
Certified Instructor, Content Developer