4的平方根是( )
A:-2
B:2
C:±2
D:±2
在一个基因库中,显性基因与隐性基因的比例相等,如果每一代隐性基因型的个体都不能产生后代,则( )
下列与水有关的说法正确的是( )
→Eating more vegetables will ____ ____ ____ to you.
下列各句中,没有错别字的一项是( )
He promised ________ his old friend during his stay in Tianjin