下列说法正确的是[ ] A．把含14N的DNA放在含15N的培养液中复制一次，子
题型：选择题
问题：
下列说法正确的是[ ]
A．把含14N的DNA放在含15N的培养液中复制一次，子代中含15N的DNA占50％
B．应用基因突变的原理进行人工诱变育种，可实现生物性状的定向改变
C．二倍体水稻体细胞有24条染色体，水稻的单倍体基因组由12条双链的DNA分子组成
D．植物营养生长是生殖生长的基础，所以营养生长越旺盛对生殖生长的促进作用越强
题型：选择题
读句子，选择适当应答语。
1.Sally, how do you get on with your new neighbor?
A. Very well!
B. Don't panic.
C. What a pity!
2. Would you like to drink some tea?
A. Thank yo u.
B. No,please.
C. I'd love to,but I had a lot of coffee just now.
3.How was your trip，Mar
y?
A. Enjoy yourselves!
B. Thank you!
C. That was fantastic!
4.Don't forget to turn off the lights before you leave the room.
A. I won't.
B. I will.
C. Thanks.
5.If you need help,you can ask Project Hope.
A. 
B. 
C. 
