A：外界声波→外耳道→鼓膜→内耳→听小骨→听觉神经→大脑
B：外界光线→角膜→瞳孔→晶状体和玻璃体→视网膜→视觉神经→大脑
C：左心室→主动脉→各级动脉→全身毛细血管网→上下腔静脉→右心房
D：外界刺激→感受器→传入神经→神经中枢→传出神经→效应器
“鱼儿离不开水”，对此最恰当的解释是 （ ）
wēi é
jùn bá
xuě lián
áo xiáng
____
chú yīng
kūn lún
yáo lán
jǐn xiù
A. How much are they?
B. Can I help you?
C. OK. We'll take them.
D. What size ?
E. Yes. But I like the blue pair.
A:____
B: Yes. A pair of shoes for my son.
B: Size6.
A: How about this pair?
B: Are they nice，John?
C:____
B: Are the blue ones all right?
C: Yes. they are.
B:____
A: They are 40 yuan.
