In which one of the following sentences is the semicolon used correctly?

A. Cheryl's favorite snack is chocolate; she could eat it daily.

B. Whenever I feel afraid; I think of Aunt Margaret.

C. Jacob, who plays in the orchestra; has a solo in the concert.

D. Donald has three sisters; Carla, Donna, and Maggie.

The correct answer is A. To use a semi colon correctly, the clauses on both sides of the semi colon must be able to stand alone as their own sentences. "Cheryl's favorite snack is chocolate" and "She could eat it daily" indeed are able to stand separate from one another, rendering the semi colon correct. B and C are incorrect because they use a semi colon as if it were a comma. D is incorrect because it's using a semi colon as if it were a colon (which often introduces a list).