在数字电路中,三极管通常被当作()使用。
A.电源
B.放大器
C.开关
D.负载
参考答案:C
While she ______ the newspaper, her sister ______ asleep. [ ]
A. read; fell
B. was reading; was falling
C. read; was falling
D. was reading; fell
溢流阀的主要作用是限制管路()。
A.最低压力
B.最大流量
C.最高压力
D.最小流量