The correct answer is B. She took a deep breath and stepped onto the sidewalk as her tears were drying.
The syntax is the study of grammatical structures in sentences, this means syntax deals with the rules and principles that guide the way language is used following specific structures including word order. Even though syntax can vary and the order of words in a sentence is not completely fixed, especially in the way real users of language use words, according to traditional syntax sentences should follow a specific order which is Subject (the one doing the action) + Verb (action) +Object (the object affected by the action).
In this way, this is the order words in a sentence should follow and the case of option B as the subject goes first, then is followed by a verb and then by an object, then a second verb is introduced and the object of it, a subject it is not placed before the second verb as the actions are connected to the first subject: She (Subject) took (Verb) a deep breath (Object) and stepped (Verb) onto the sidewalk as her tears were drying (Object). Thus, B is the sentence that follows the traditional syntax structure as it follows subject + verb + object.