A:利用秋水仙素处理萌发的种子或幼苗,得到多倍体植株
B:利用花药离体培养得到单倍体植株
C:利用基因工程培育抗棉铃虫的棉花植株
D:利用细胞工程培育“番茄-马铃薯暠杂种植株
They saw the missing boy ______ near the river at that time.