People often think they are energetic and healthy and don’t need exercise I have to wa

问题补充：

People often think they are energetic and healthy and don’t need exercise. , I have to warn that it is completely wrong.

A. However

B. Therefore

C. Otherwise

D. Meanwhile

答案：

(答案→)A. However

B. Therefore

C. Otherwise

D. Meanwhile

解析：A然而；B因此；C否则，要不然；D与此同时；句意：人们经常认为自己精力充沛很健康，不需要锻炼，然而，我不得不警告这是完全错误的。根据句意可知A项表示上下文的转折关系。故A正确。