she then purchased him a pair of shoes,and tying up the remaining pairs of socks为什么type不是加d.and不是并列吗

你的问题有错误 你在仔细看看

原句如下：Placing a pair upon the boy‘s feet， she then purchased him a pair of shoes， and tying up the remaining pairs of socks， gave them to the boy.

gave前面省略了 she. 现在你就应该明白了：并列的是两个句子。 两个句子中，placing 和 tying 都是动词的 ing 形式作状语。

and并列的 是两个谓语 第一个谓语是 purchased 第二个谓语是gave
现在分词短语 tying up the remaining pairs of socks是第二个谓语gave 的 状语
原句是 Placing a pair upon the boy's feet,she then purchased him a pair of shoes,and tying up the remaining pairs of socks,gave them to the boy.

是tie 吧
这里是非谓语的范畴
虽然有and 连词，可是没有主语，其实主语是she,she 和tie 之间是主动关系，所以用现在分词，tying
时态还是过去式，
and tying up the remaining pairs of socks
= and she tied up the ....