Find a mistake in each sentence:1. How many students

Find a mistake in each sentence:
1. How many students in this class?
2. Its a park next my house.
3. There isnt any sandwiches.
4. There are a notebook, keys and mobile in his briefcase.
5. There is a dictionary in your bag?
6. This is a cat in front of the fireplace.
7. There be a lot of photos of us in my web page.
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