Which sentence is most clearly written?

The second sentence is the most clearly written because it presents the information in a straightforward and concise manner. It starts with the subject, "Calvin," followed by the verb "denied," and then directly states the assertion about him not being the assailant. This structure allows readers to quickly understand the main point without unnecessary complexity.

In contrast, the first sentence, while grammatically correct, uses a less common phrasing, "that the assailant was he," which can be awkward and potentially confusing for readers. The phrase “was he” can sound formal or stilted in everyday language, making the sentence feel less accessible. Clarity often comes from simple and direct language, which is embodied in the second sentence.