撒哈拉以南的非洲分布最广的气候是[ ]
A、热带雨林气候
B、热带沙漠气候
C、热带草原气候
D、地中海气候
答案：C
All human beings have a comfortable zone regulating the ________ they keep from someone they talk
with.[ ]
A. distance
B. scope
C. range
D. boundary
试述切削深度、进给量、切削速度对切削温度有何影响规律？
