题干
——Can I join their club?
——I am afraid you will be refused __________ you've passed all their tests.
A：if
B：when
C：unless
D：since
答案(点此获取答案解析）
C
——Can I join their club?
——I am afraid you will be refused __________ you've passed all their tests.
A：if
B：when
C：unless
D：since
气体的体积（V）与时间（t）关系如右图。反应中镁和铝的