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Question focus: Correct usage of whose and adjective clauses with quantifiers.
In this question, we want to talk about many of Ayn Rand's novels in the adjective clause. So we have several things happening at once in this question. First, we are are talking about Ayn Rand's, not Ayn Rand. When we need to use the possessive form in an adjective clause, we have to use whose. Next, we need to use a quantifier to talk about a certain portion of the novels. The proper way to use quantifiers is to use the quantifier with of.