7. —Which T-shirt do you like best?
—Sorry, I can't which one to buy now.

decide

本题属于字母D开头的词汇考查，结合对话语境，问句询问最喜欢哪件T恤，答句要表达“我现在没法决定买哪一件”的含义，情态动词can't后需要接动词原形，符合语义且以D开头的单词为decide，意为“决定”，符合语法和题目专题要求。

8. His father the whole family to the market this afternoon, and
they bought a lot of things there.
9. The teacher the cake six parts and gave them to six children.
10. The crow（乌鸦） picked up a small stone and then it into the bottle.

8. drove
9. divided; into
10. dropped

这组题目考查字母D开头的词汇和一般过去时的用法：
1. 第8题：句中时间状语this afternoon以及后句的bought（buy的过去式）表明动作发生在过去，需要填D开头的动词过去式，drive sb. to sp.表示“开车载某人去某地”，其过去式drove符合句意。
2. 第9题：后句的gave（give的过去式）表明动作发生在过去，固定搭配divide sth. into...表示“把某物分成……”，divide的过去式divided符合“老师把蛋糕分成六份分给六个孩子”的语境。
3. 第10题：and连接并列谓语，前面的picked是pick的过去式，这里需要填D开头的动词过去式，drop sth. into...表示“把某物扔进……”，drop的过去式dropped符合乌鸦往瓶子里丢石头的语境。