A. Gilda attends college; thus, she also works full-time at an engineering firm.
B. Gilda is a hardworking student; therefore, she earned a good grade on her essay.
C. Gilda likes math class; nevertheless, she enjoys anything pertaining to numbers.
D. Gilda lives near campus; likewise, the grocery store is not within walking distance.
Therefore is used to affirm the first part of the sentence into showing why the second one should be mentioned.
Therefore, the Correct Answer is B.