研究传染病的动物模型是（）
A．无菌动物
B．悉生动物
C．无特殊病原体动物
D．清洁动物
E．常规动物
参考答案：B
加速试验与长期试验要求用（）批供试品进行。
—What did the doctor say? —He asked how long _________.
A．has my daughter caught a cold
B．had my daughter caught a cold
C．my daughter had caught a cold
D．my daughter had had a cold
