The old couple decided to ______ a boy and a girl though they had three of their own
A.adaptB.admitC.abandonD.adopt在线课程D
解析：
考查词义辨析。adapt适应，admit 承认，abandon 舍弃，adopt 采纳，收养，句意：这对老夫妇决定收养一个男孩和一个女孩虽然他们已经有自己的三个孩子了。所以选D。