题干
In summer milk will quickly go bad_____ it is put into a fridge.
A：though
B：unless
C：because
D：once
答案(点此获取答案解析）
B
In summer milk will quickly go bad_____ it is put into a fridge.
A：though
B：unless
C：because
D：once
，神州飞船在地球表面附近圆形轨道运行周期为
，火星质量与地球质量之比为p，火星半径与地球半径之比为q，则
