As Susan stared at ______ piles of plastic in her recycling bin, ______ strong sense of responsibility made her stick to her recycling work．

A．不填；不填

B．不填; a

C．the ; a

D．the; the

铜合金属于（）

A.高熔合金

B.中熔合金

C.低熔合金

D.锻制合金

E.焊合金