one is fully prepared, outdoor sports can sometimes mean injuries. A．Until B．Bec
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________ one is fully prepared, outdoor sports can sometimes mean injuries.
A．Until
B．Because
C．When
D．Unless
试题答案
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……”。