在不引起误解的情况下，剖切平面转折处的字母可以省略。（ ）
查看答案
剖切符号的转折处不允许与轮廓线重合。（ ）
A. 对
B. 错
Cotton became the most profitable crop in the South mainly because of the——
A. use of irrigation on plantation
B. Whitney’s cotton gin
C. slave labour
D. improved agricultural techniques
Gold was discovered in California in ——————
A. 1828
B. 1838
C. 1848
D. 1858
微信支付 
支付宝支付