单项选择。
In the tree many birds. [ ]
A. have
B. has
C. there are
D. there is
答案：C
清晨现象（dawnphenomenon）
硝酸甘油治疗心绞痛
A．首剂减半量B．首剂加倍C．早晨一次顿服D．门服用药E．舌下含服
