is加现在分词是什么时态

句型分析：

1、一般疑问句是将be动词移到主语前面，句末加问号，读升调。

be+主语+doing sth

Are they putting up the scaffolding? Yes, they are. / No, they aren't.

Is he showing a foreign guest round the city? Yes, he is. / No, he isn't.

2、否定句式是在be动词后加not。

主语+be+not+doing sth

I am not working.

He isn't running on the track.

The students aren't playing football.