疑问词+不定式，是特殊不定式，即名词性疑问分句的简略形式，名词性疑问分句省略了主语+情态动词，不定式的to还原。这种不定式只能做名词性成分。

what coverage to buy, what amounts of insurance to buy, and what agent and company to buy from.

= what coverage they should buy, what amounts of insurance they should t buy, and what agent and company they should buy from.