"doing"在句子中可以作不同的成分，主要包括以下几种：

动名词（Gerund）

作主语：Reading books broadens our horizons.

作宾语：I enjoy reading.

作表语：Her work is selling the computers.

作定语：Swimming is my favorite sport.

现在分词（Present Participle）

表示主动或正在进行的动作：I am doing my homework.

作定语：The crying baby needs attention.

作状语：She is busy doing her homework.

作宾语补足语：I saw him doing something strange.

动词不定式（Infinitive）

具有名词、形容词和副词的特征：To learn English well is important.

作主语：To get good grades, we should study hard.

作宾语：I want to go home.

作宾语补足语：The teacher asks us to read English every day.

作定语：I have a lot of homework to do.

过去分词（Past Participle）

表示被动：The book was written by a famous author.

这些例子展示了"doing"在不同语境下的多种用法，希望对你有所帮助。