特发性肺间质纤维化的病因为（）
A.真菌感染
B.粉尘沉积
C.大气污染
D.肿瘤浸润
E.不明原因
参考答案：E
区际法律冲突
_____ is the population of China? It is about 1,300,000,000.
A．How many
B．How much
C．What
D．How
