1.动词四中表达中的doing（一人）
A、做一件事：doing“分词”
A flying tyger.
B、做二件事：doing做“进行式”
At half past nine last night, I was doing my homework.
2.一人：have（has、had）
A、时态~助词
I have eaten a breakfast now.
B、情态~动词
I have to leave。
C、使役~动词
③具有情态动词特征：have(had,has) to,used to, ought to
④可做情态动词又可作助动词：如：shall(should),will(would)[1]
