人体排出的废物都必须经过适当的处理，才不至于污染环境，同时还能变废为宝。[ ]
√
Sometimes they may play to passers-by in the street or subway so that they can earn some______ money for themselves or to pay for their instruments.
A．certain
B．extra
C．various
D．unusual
普通PC声卡中的DA转换器最为接近的转换速率是（）。
A.44kHz
B.144kHz
C.288kHz
D.8MHz
