纤维横截面含有两种或两种以上成分或组分的化学纤维称为()。
A.复合纤维
B.异形纤维
C.合成纤维
参考答案:A
施工现场,在机械化土石方开挖时,需挖掘机操作人员、卡车司机、工长、( )和普工。
A.压路机操作人员B.爆破工C.钢筋工D.机修工
The GMDSS must combine all various subsystems, because().
A.they all have different limitations with respect to coverage
B.they all have different limitations in the technology they use
C.different systems apply to different ships
D.all of above