Query about Question 1 from "(I'm Overwhelmed) Arithmetic Progress Quiz #4" [6829]

GRE GRE Quant Problem Solving
1

https://www.gregmat.com/quizzes/quiz/im-overwhelmed-arithmetic-progress-quiz-4 (Question 1)

If 3n+3 is a multiple of 3 wouldn’t the answer be A?

2

Why does it have to be a multiple of 3 specifically?