here is my old friend.(副词)
The woman with a baby in her arms is my sister. (介词)
The boys playing football are in Cla2. (现在分词)
The trees planted last year are growing well now. (过去分词)
I have an idea to do it well. (不定式)
You should do everything that I do. (定语从句)
七、主语(subject): 句子说明的人或事物。
The sun rises in the east. (名词)
He likes dancing. (代词)
Twenty years is a short time in history. (数词)
Seeing is believing. (动名词)
To see is to believe. (不定式)
What he needs is a book. (主语从句)
It is very clear that the elephant is round and tall like a tree.
(It形式主语,主语从句是真正主语)