A:HF溶液
B:KOH溶液
C:盐酸
D:水玻璃
复印机使用过程中会排放出对人体有害的气体是( )?
化简:(1+1x)÷x2-1x的结果为( )
-- Did you hear anything ____ (usual) in the next door?
-- No, I was chatting online with friends.