人类对遗传物质本质的探索经历了漫长的过程,下列有关叙述正确的是( )
A:孟德尔发现遗传因子并证实了其传递规律和化学本质
B:噬菌体侵染细菌实验比肺炎双球菌体内转化实验更具说服力
C:沃森和克里克提出在DNA双螺旋结构中嘧啶数不等于嘌呤数
D:烟草花叶病毒感染烟草实验说明所有病毒的遗传物质是RNA
A: Hi, Mum! ____
B: Yes, I can.
A: ____
B: At Tian' anmen Square.
A: Great. ____
B: I m walking around. There are lots of people here.
A: Oh, what is my father doing?
B: ____
A: Have a good time.
B: Thank you! ____
A: Bye!
A. He is buying some presents.
B. What are you doing?
C. Goodbye!
D. Where are you?
E. Can you hear me?
下列说法正确的是( )
5+1=6 6-1=5
1+5=6 6-5=1
柑橘主要分布于我国南方,苹果主要分布于我国北方,造成这一分布差异的主要生态因素是( )