-Hello, may I speak to Mr. Smith?-Sorry, he isn't in. He__________ the office.
A:has been to
B:has gone to
C:has been away
脱式计算(能简算的要简算)
711 ÷9+ 19 × 411
12.69﹣4.12﹣5.88
0.6×3.3+ 35 ×7.7﹣0.6
( 14 + 18 )×24× 19 .
用推拉注射器活塞的方法可以检查下图装置的气密性。当缓慢拉动活塞时,如果装置气密性良好,则能观察到