消防泵的效率是指流过消防泵的液体在单位时间内从泵中获得的能量。
参考答案:错
—____ you stay at home last week?
—Because l was ill. [ ]
A. What did
B. Why did
C. Why were
D. Where did
开启过的疫苗,有效时间正确的是()
A.室温24小时
B.室温6小时
C.室温2小时
D.冷藏6小时