语法总结
Is/Are ... doing?
用 Is/Are ... doing? 询问某人是否正在做某事。
例：Is he watching TV? Yes, he is.
现在进行时的一般疑问句
be 动词提到主语前，动词使用 -ing 形式。
例：Are they playing basketball? No, they aren't.
There is/are
there is 后接单数，there are 后接复数。
例：There are some students outside.