OA is A

OE is

The original sentence is correct as written. The participle resorting is correct because it describes the networking websites. The gerunds advertising and cross-selling are correct because they indicate two things that the business models are based on. Finally, the infinitive to generate correctly indicates how the networking websites use the business models (to generate revenue).

Choice B introduces an error by including "which;" the adjective clause now modifies innovative ways instead of networking websites. The original sentence describes a contrast between two opposite actions, namely capitalizing in innovative ways and resorting instead to traditional business models. By including "which," Choice B eliminates this contrast and makes the sentence illogical.

Choice C introduces a parallelism error because the gerund advertising is not in the same form as the infinitive to cross-sell, but both are meant to describe the two things that the business model is based on.

Choice D introduces an error by replacing the participle resorting with the infinitive to resort, which cannot properly modify networking websites. Furthermore, in the original sentence the business models are only based on advertising and cross-selling, but when all three items are parallel, the sentence suggests that the business models are based on three things: advertising, cross-selling, and generating revenue from their members. However, it does not make sense for a business model itself to have members. The original sentence makes it clear that the networking websites use those "captive audience" business models to generate revenue from the websites' members.

Choice E connects the dependent clause (resorting instead to...) to the main clause (online social networking websites have yet to capitalize...) by a comma plus a coordinating conjunction (and), but a comma plus a coordinating conjunction can only connect two independent clauses.

Choice A is correct.