有毛丝的丝饼要降为C级。
参考答案:错
Everyone tells me I’m a good speaker, _____ I really don’t like speaking in public.
A.and
B.so
C.but
D.or
绞车摆放时,使滚筒轴线垂直中心线正对井口,保证哪三点成一线?