人类气体交换的场所是？（ ）
A：肺
B：气管
C：肺泡
D：支气管
如图，在下列条件中：①∠DAC=∠ACB；②∠BAC=∠ACD；③∠BAD+∠ADC=180°；④∠BAD+∠ABC=180°．其中能使直线AB∥CD成立的是____ ．（填序号）
已知a，b为实数，则解可以为–2＜x＜2的不等式组是（ ）
You are discussing the following picture with your English friend Jim. Now you are telling him how you understand the picture and what makes you think so.
