谓语是is.这种句子是主系表结构。即，主语加系动词做谓语，，再加其他的名词或者形容词或者动名词短语作表语。另外这个句子中it 有时也可以做形式主语。例如

It is clear ( obvious, true, possible, certain....) that .....

该句型中it是形式主语，真正的主语是that引导的主语从句，常译为＂清楚（显然，真的，肯定．．．）＂

1.It is an Englishbook.句子中谓语动词是is.汉语意思是它是一本英语书。

2.英语学习中做谓语动词的有实义动词do read 等还有be动词am is are.

3.We are students. ！Are you a teacherYes,I am.I like English very much.Do you like EnglishNo,I don't.Yes,I do.