双链DNA分子中正确的碱基配对方式是( )
A:C与C配对
B:G与G配对
C:T与T配对
D:A与T配对
His grandfather ____ ____ a lot of hardships during the war.
一枝蜡笔的体积大约是9____
一个热水瓶大约能盛水2____