What is the correct punctuation in this sentence: "The first part of the test was on chemistry, the second on mathematics, and the third on english."?

The correct punctuation choice maintains parallel structure and properly capitalizes "English." In this context, the series composed of "the first part of the test was on chemistry, the second on mathematics, and the third on English" effectively emphasizes the different subjects being tested.

Using a comma before "and" in this series clarifies that the phrase "the second on mathematics" is distinct from both "the first part of the test was on chemistry" and "the third on English," thereby enhancing readability. The conjunction "and" connects the final item smoothly, which is consistent with how lists are typically punctuated in English.

Additionally, capitalization is essential for "English," as it is a proper noun that refers to a specific language, unlike "mathematics," which, although it can be capitalized in certain contexts, is not in this case given it is not being presented as a proper noun in the context of the sentence. Thus, the structure and punctuation effectively communicate the information clearly and correctly.