种子的休眠
参考答案：具有生命力的种子，由于种皮障碍、种皮尚未成熟或种子内含有抑制物质等原因，在适宜萌发条件下，也不能萌发的现象。
Look and choose the right sentence．（看图选择合适的句子。把句子的序号填入图片下的括号内。）
1. Is Line A shorter than Line B?
2. It's very hot. Why don't you go swimning?
3. Is Circle A smaller than Circle B?
4. Why don't you buy a Chinese kite?
5. This tree isn't taller than that one.
6. There are four cakes in the picture.
超声波检查方法怎么分类？
