Quote:
Common stocks, which are shares of ownership in a corporation, is the most direct way to participate in the fortunes of a company.
A. is the most direct way to participate in the fortunes of a company
B. is the most direct way for participating in the fortunes of a company.
C. is the most direct way of participating in the fortunes of a company.
D. are the most direct way to participate in the fortunes of a company.
E. are the most direct way for participating in the fortunes of a company.
The first split is between "is" and "are"- i.e., singular vs plural. So, the first thing to determine is whether "Common stocks" is being treated in a singular or plural context. In such cases - i.e., for collective nouns - always check the non-underlined portion for clues. Here, in the non-underlined portion contains the plural reference "which..
are.." to refer to "Common stocks". Hence the subject is being treated as a plural noun, and the verb must be plural. This eliminates A, B, and C
Between D and E - the main split is between "to participate" and "for participating". In general, all things being equal, whenever we have a split between to+verb form and [preposition] + "-ing" form, we prefer to go with the to+verb form, especially when we want to indicate a purpose/intent. This is because the "for + -ing" construction does not indicate purpose as precisely and/or directly as the to+verb form.
For example, consider this sentence:
John went to the office
to complete/for completing his task : the to+verb form automatically sounds more intuitive and direct.
This eliminates option E, and leaves us with option D as the best answer.