中国各民族的居住形式大体有三种类型：（）
参考答案：帐篷型；干栏型；栋宇型
When I entered the step-classroom (阶梯教室), the lecture __________ and the audience __________ attentively.
A．began, listened
B．was begun, was listening
C．had begun, listened
D．had begun, were listening
粒细胞缺乏症可出现的临床表现是（）
A．进行性贫血
B．皮肤、鼻腔等处发生坏死性溃疡
C．皮肤、黏膜出血
D．频繁性呕吐
E．胸骨压痛
