对于肺癌的转移，下列哪个描述不正确
A．转移较快、较多见B．淋巴道转移首先至颈部淋巴结C．血道转移常见于脑D．早期肺癌无淋巴结转移
参考答案：B
如图所示，甲、乙两个门窗紧闭的房间里各有一位同学，乙房间的玻璃是双层的，中间抽成真空。
（1）甲、乙两个房间的同学都能看见树上的小鸟，这是为什么？
（2）但乙房间的同学听不到小鸟的“歌唱”，又是为什么？
41. If it ______ for the fence, he ______ into the river.
A. were not; fallen B. had not been; could have fallen
C were not; could fall D. had not been; could fall
