PCM均匀量化信噪比随着（）增大而增大。
A.量化台阶
B.量化级数
C.噪声功率
D.采样频率
参考答案：B
---Do you mean he ______ lots of money on books?
---Yes. They ______ him plenty of money.
A．pays, takes
B．spent, cost
C．spent , buy
D．takes, cost
一氧化碳中毒的主要诊断依据是
A．血液中氧分压下降
B．血液中胆碱脂酶活性降低
C．碳氧血红蛋白化验阳性
D．血液中还原血红蛋白超过50g/L
E．血液中血红蛋白量小于70g/L
