Answer: C. The baseball player hit the ball, and the crowd cheered.
Step-by-step explanation: When we have a sentence with two independent clauses (phrases that have complete meaning on their own) we can join them in two ways: using a comma followed by a conjunction ( "The baseball player hit the ball, and the crowd cheered"), or with a semicolon and no conjunction ( "The baseball player hit the ball; the crowd cheered"), so, fro the given options, the correct answer is option C.