A:利用克隆技术培育良种奶牛
B:将根瘤菌的固氮基因转移到小麦细胞内
C:利用组织培养技术培养蝴蝶兰
D:利用酵母菌发酵制作酒酿
He was growing a variety of ____ (胡萝卜) in the garden when I visited him.
已知1+2×3+3×32+4×33+…+n×3n-1=3n(na-b)+c对一切n∈N+都成立,则a、b、c的值为( )
人体的性别决定开始于( )