The answer is D. As her leg jiggled up and down, she chewed a ragged nail and checked her watch.
Explanation:
Syntax is a component of language that focuses on the arrangement of elements or structures used to convey ideas. Traditional syntax follows the subject-predicate structure; this means the agent of the action is followed by the action. This arrangement can be seen in the section "she (subject) chewed (verb) a ragged nail and checked (verb) her watch".
Besides this, to preserve the traditional structure other details such as complementary clauses are usually placed at the beginning and separated by a comma or similar punctuation. This occurs in "As her leg jiggled up and down" because this detail complements the sentence and is placed before the main clause separated by a comma.
