制作一个底面直径20cm、长50cm的圆柱形通风管,至少要多大的铁皮?
2×3.14×(20÷2)×50=3140(cm2)
任脉又称()。
A.阳脉之海
B.阴脉之海
C.气海
D.血海
E.髓海
The hotel porter ______ anybody who wasn't wearing a collar and tie.
A.turned to
B.turned off
C.turned away
D.turned up