尘肺病的发生与工人接触矿尘的时间长短没有关系.
参考答案：错
This college allows students to develop their own interests, to ______extent they wished. [ ]
A. whoever
B. whatever
C. however
D. whenever
动特性是用来表示弧焊电源对负载瞬变的快速反应能力。( )
