i reading a book.的i后面为什么要加am?

i reading a book.的i后面为什么要加am? I am reading a book 英语翻译I am reading a book loudly. I am reading a book .对reading提问 为什么I后面要加am? I am reading an (i ) book book am a reading i连词成句 i am reading a book.改为一般疑问句 I am reading a book ( ) the history of the world i am reading a book.改为肯定句 No,I am reading a comic book.问句 I am reading a book.(改为否定句）