骨髓瘤好发于下列哪些部位（）
A.肱骨
B.脊椎
C.肋骨
D.骨盆
E.胸骨
参考答案：B, C, D, E
—Would you like to drink ________ hot drinks?
— No, thanks. There is _________in my cup.
A．any; any
B．some; some
C．some; any
D．any; some
蜗杆传动的自锁现象是指什么？在什么条件下会产生自锁？
