单项选择题 胸内负压是实现肺通气的重要条件。

未知题型 From the missionary's manuscript. we may infer that ______.A.the great signal drums were very popular thereB.people there were hostile to the European strangersC.the Amazon River area was densely populated thenD.the tribes along the river were always at odds

单项选择题 熊彼特认为：引入一种新产品或者新的特性被成为( )。 A 产品创新 B 工艺创新 C 开发新的资源创新 D 市场创新