Mr. Brown doesn’t feel at _______ease for the time being for _______ little money the present job     brings him can hardly support his extended family.

A．/; the

B．an; the

C．an; /

D．the; a

预测发生一级反应的药物，其半衰期

A．与初始浓度Co无关

B．与t时反应物浓度有关

C．与反应常数k无关

D．与初始浓度Co有关

E．与反应时间有关