为强效，长效抗炎镇痛药（）
A．青霉素V
B．苯唑西林
C．替卡西林
D．哌拉西林
E．舒巴坦
参考答案：D
Helen is 15 years old, and Joan is 15, too. So Helen is________Joan.
A．as big as
B．as older as
C．as old as
D．so old as
设y1=xex+2e2x，y2=xex+3e-x，y3=xex-e2x-e-x为某二阶常系数线性非齐次方程的三个特解，设该方程的y"前的系数为1，则该方程为______．
