A:p
B:b
C:d
D:q
将下图中有关植物体的结构层次填写完整.①____;②____;③____;④____;⑤____.
兴奋在神经元之间传递的结构基础是突触,突触的结构包( )
With the loss of labor,the old farmers ________at home had to choose less laborintensive crops.