It's B.teacher because it is a specific person.
<h2>Answer:</h2>
If linking words start a sentence, they are followed by a comma. When they are used to connect two clauses, a semi-colon is used at the end of the first clause, and a comma is often used after the linking word(s).
The correct answer is B. The river deposited debris at every turn. There is a verb, a subject and an object, so it is considered a full sentence.
