曲面锉削的方法有()。
A.顺向锉
B.外圆弧面的锉削
C.内圆弧面的锉削
D.交叉锉
参考答案:B, C
生活在沙漠中的仙人掌,叶退化成刺可以减少水的散失.对此最恰当的解释是( )
A.生物影响环境
B.生物适应环境
C.生物改变环境
D.生物依赖环境
They had to ______ the meeting because the organizers didn’t prepare the hall well, where people can share their opinions and hold discussions.
A.put forward
B.put out
C.put up
D.put off