A:转基因作物可通过花粉扩散到它的近亲作物上,可能出现对农业不利的“超级植物”
B:杂草、害虫从它的近亲获得抗性基因,可能破坏生态系统的稳定性
C:转基因必须在人为控制下才能完成,自然条件下基因污染是不增殖和不被扩散的
D:转基因食品转入的蛋白质是新蛋白时,这些异种蛋白有可能使人引起食物过敏
根冠的外层细胞不断磨损,但根冠从不会因磨损而消失,原因是( )
竖直放置的下端扎有橡皮膜的开口玻璃管内,倒入一定量的水后,橡皮膜向外突出,当将管子逐渐倾斜的过程中,管底的橡皮膜凸起程度将( )
We go shopping on Sunday. My father likes fruits very much. We buy some bananas and red apples at the fruit shop. My mother likes to wear new clothes. She buys a new sweater and a new skirt at the clothes shop. I buy three books at the book shop. At last(最后),we buy some tea for my grandfather in a tea shop.