手持式或支架式钻、携带式仪器的外壳可用轻合金制成，容积不大于2L的外壳可用（）制成。
A.塑料
B.铜材
C.铸钢
D.铸铁
参考答案：A
Though ________ to a higher position, she still didn't content herself. [ ]
A. promoting
B. being promoted
C. having promoted
D. promoted
减摩摩擦
