刮板输送机发生刮板链在底槽出槽故障的原因可能是（）。
参考答案：输送机本身不平直
.
Joe’s_______ in the get-together surely brought us a lot of pleasure as he is a man with a
strong sense of humour.
A．joining
B．having been joined
C．joined
D．had joined
「手紙」的意思是（）。
A、手纸
B、邮件
C、短信
D、信件
