Explanation

Creating a filter: there's a problem with the original sentence: the phrase "which measures" appears to point back to "species of whales," but that's against the intended meaning of the sentence.

Applying the filter: scanning the answer choices, we see (B) retains the problem, so (B) is out. Choice (D) has defects: "though not in fact a whale" should modify a noun set off by a comma but instead drives into a clause with a subordinate conjunction; that's ungrammatical. Choice (E) is an inferior version of (C) with an unnecessary gerund, "being." The correct answer is (C).