________ one is fully prepared, outdoor sports can sometimes mean injuries.
A.Until
B.Because
C.When
D.Unless
________ one is fully prepared, outdoor sports can sometimes mean injuries.
A.Until
B.Because
C.When
D.Unless
D解析:句意:除非有充分准备,否则户外运动有时会意味着受伤。根据语意选D项,表示“如果不……;除非……”。