Which sentence is most clearly written?

The sentence stating that "A clear understanding of the law is necessary for every police officer" is most clearly written because it adheres to conventional grammatical structure and prioritizes clarity. The phrase "a clear understanding" clearly establishes the concept being discussed, emphasizing the necessity and the importance of comprehension in a straightforward manner.

This construction makes the subject of the sentence—understanding the law—immediately accessible and easy to grasp. By placing "clear" before "understanding," it reinforces the idea that not just any understanding will suffice, but rather a clear and thorough comprehension is essential for police officers.

In contrast, the other sentence, while still conveying a similar idea, uses "understanding the law clearly," which can introduce ambiguity regarding what is meant by "clearly." This phrasing could suggest that the manner in which the law is understood might be subject to interpretation, which detracts from the intended impact of the statement. The focus shifts from the necessity of a solid comprehension to the method of understanding, making it less direct and potentially confusing for the reader.