【题目】_____you take an active part in physical activity _____be able to keep fit and stay healthy.
A.If only; you will
B.If only; will you
C.Only if; you will
D.Only if; will you

【答案】D
【解析】考查部分倒装。句意：你只有积极参加体育锻炼，你才能保持身体健康。If only固定短语“要是......”，句子用虚拟语气；only +状语位于句子开头，句子用部分倒装。故选D。