海面测量船的声呐测出其发出超声波到海底至接受到回声的时间t就可以确定海面到海底的深度,若所测出海底某处的时间t为4s,声音在海水中的传播速度取1500m/s,那么海底深度为多少? 答案:解:超声波从海面到海底用的时间: t= {#mathml#}12{#/mathml#} ×4s=2s,由v= {#mathml#}st{#/mathml#} 可得,该处海水的深度:h=s=vt=1500m/s×2s=3000m.答:海底深度为3000m
-Hi, Tom, can I use your iphone for a while this afternoon?
-Sorry._________.
[ ]
A.
it’s repaired
B.
it has been repaired
C.
it’s being repaired
D.
it had been repaired