The subject is not "hours," but "the number," which requires a singular verb. Eliminate choice (A). Now you know that "lend" should be "lends." If you didn't see this up front, a quick scan of the beginning of each choice reveals that subject-verb agreement is an issue.
The singular noun "number" goes with the singular verb "lends" in (B), (C), and (E). So we can eliminate (A) and (D). It's not the "observation of many managers" that's under discussion. It's the observation that many managers pine for a six-day work week. Select (E).