题目

 He hated the war so much that he decided to leave the army _____. A. for long    B. once in a whileC. for good    D. once upon a time 答案：C5．已知数列{an}的通项公式是an=$\left\{\begin{array}{l}{3•{2}^{n-1}（n是偶数）}\\{3n-2（n是奇数）}\end{array}\right.$，则a3+a4=（　　）A．34B．31C．22D．19