锯割时，起锯行程要短，压力要小，速度要慢。起锯角约（）左右。
A.10°
B.15°
C.20°
D.25°
参考答案：B
The garden _______ while they were away from here. [ ]
A. took good care of
B. was taken good care
C. was taken good care of
D. was taking good care
一列240m的列车通过一座1500m长的大桥，车过桥的速度为30m/s，求：
（1）列车完全通过大桥需要的时间；
（2）列车全部在桥上行驶的时间．
