“试管婴儿”的培育诞生和嫁接繁殖无核蜜橘在生物学上依据的原理依次是( )
A:无性生殖,有性生殖
B:有性生殖,无性生殖
C:克隆技术,转基因技术
D:转基因技术,克隆技术
Lots of university students practice _______ English _______.
My teacher promised to ______ my suggestions, so I gave him some ______.
5+____=11
4+____=13
一个几何体及它的主视图和俯视图如图所示,那么它的左视图正确的是( )