Explanation

Creating a filter: in the original sentence, the phrase "despite its being soft enough to grow" grammatically modifies "human," and that's not the intended meaning. The skull of the newborn is what's soft, according to the intended meaning. We eliminate (A) and go straight to the other answer choices to eliminate others with modification errors.

Applying the filter: as it turns out, (B) through (E) are all free of the error in (A). So we'll move straight to finding defects in the other choices.

Finding objective defects: choices (B) and (C) use the gerund unnecessarily in the phrase "despite being," so we focus on (D) and (E), which end differently. The phrase "but rather" is clear in this case, in which we are saying the baby's skull is not one thing, but rather another. Since the word "but" alone can mean different things, we prefer to use "but rather" when relevant for clear meaning, though it's not an absolute requirement. Choice (E) is scarcely flawed, but (D) is objectively clearer and still succinct. The correct answer is (D).