---Did you watch the programme I’m a singer on Friday night? It was wonderful.

---I wish I had, but I _______for the mid-term examination.

A．was preparing

B．prepared

C．had prepared

D．would prepare

能使虫体肌细胞去极化，增加放电频率，使虫体肌肉收缩的药物是：

A．哌嗪
B．左旋咪唑
C．噻嘧啶
D．槟榔
E．甲苯咪唑