把问题和答语对应起来。
A.He's from China.
B.He's my teacher.
C.No, she is old.
D.He's short and thin.
E.No, he is old.
已知小麦抗锈病是由显性基因控制,让一株杂合子小麦自交得F1,淘汰掉其中不抗锈病的植株后,再自交得F2,从理论上计算,F2中不抗锈病占植株总数的( )
长城总长约6700010米,用科学记数法表示是(保留两个有效数字)( )