【题目】Sometimes tests are needed _________ doctors discover exactly what's wrong with your body.
A. since B. before
C. although D. if
在线课程【答案】B
【解析】
考查连词。A. since 因为，由于；B. before在……之前；C. although虽然，尽管；D. if如果。句意：有时在医生准确发现你的身体出了什么问题之前做检查是必要的。根据前后句的关系，我们可以判断出检查应在医生诊断之前，故选B.