Answer:
C. He stood up
Explanation:
An independent clause is a statement that can stand alone and still make sense. Out of all the answer choices given, only 'C' expresses a complete thought as it contains a subject and a verb. The subject being 'he' and the verb 'stood up.' In addition, looking at the other choices can easily be seen that they don't really make any sense when read aloud, since it does not depict a complete thought.