A hearty laugh relieves physical tension your muscles relaxed for over half an hour.A. to

问题补充：

A hearty laugh relieves physical tension, your muscles relaxed for over half an hour.

A. to leave

B. left

C. leaving

D. leave

答案：

A. to leave

B. left

(答案→)C. leaving

D. leave

解析：考查现在分词做结果状语，句意：一个开心的大笑可以缓解身体的紧张，使肌肉放松半个小时。一个开心的大笑的结果是使肌肉放松半个小时。属于顺理成章的结果，用现在分词做结果状语，选C。