You have to wear a helmet and a life jacket for protection just you fall into the water.

问题补充：

You have to wear a helmet and a life jacket for protection, just you fall into the water.

A. for

B. because

C. so that

D. in case

答案：

A. for

B. because

C. so that

(答案→)D. in case

解析：考察连词，for 因为， because因为 so that 为了，以致于 in case万一

句意为你一定要带一个头盔，穿一件救生衣，只是以防万一你掉到水里。