Sentence A - Among the top bosses are Can match with a mention of the top bosses as an example (Among the top bosses are X and Y) or a clause with relative pronoun (Example - Among the top bosses who are X and Y, will be attending the meeting etc). D, E and F don’t fit this criteria. Hence, there is no pair here. Sentence B - Though there aren’t many philanthropists these days Can match with an independent clause only and introduce a contrast to the fact that there are less philanthropists (those who donate). E and F are independent clauses but they don’t make logical sense as they don’t convey philanthropy but simply mention registering of companies. Hence, there is no pair here. Sentence C - For that reason, Can match with an independent clause only. “For that reason” is open ended here and anything can fit in. E and F are independent clauses. Thus, C-E and C-F are the correct pairs.