Question

Mike+is+watching+TV+now改为否定句？

Answer 1

英语中陈述句变否定句要注意以下三个方面：
1、陈述句中的谓语部分有be动词、助动词或情态动词，直接在这些词后加not即可。
如:
He is a student.
He is not a student.
He has studied English for 10 years.
He has not studied English for 10 years.
He can speak English.
He can not speak English.
2、陈述句的谓语部分只有实义动词。要分情形而定。
1）陈述句为一般现在时，主语不是第三人称单数。在谓语动词前加don't。
I study English every day.
I don't study English every day.
2）陈述句为一般现在时，主语是第三人称单数。在谓语动词前加doesn't，原陈述句的谓语动词改为原形形式。
He studies English every day.
He doesn't study English every day.
3）陈述句为一般过去式。在谓语动词前加didn't，原陈述句中的谓语动词改为原形形式。
He studied English yesterday.
He didn't study English yesterday.
3、肯定句中的some在否定句中应改为any
如：There are some students in the classroom. There are not any students in the classroom.
题目
Mike+is+watching+TV+now
中有助动词is（辅助构成现在进行时），属于第一种情形，直接在助动词（is）后加not即可。
Mike is not watching TV now.

Answer 2

Mike isn't watching TV now.

Answer 3

Mike isn't watching TV now