Present Simple
The dog is in the yard.
Is the dog in the yard? Yes,it is.No,it isn't.
The dog is not in the yard.
Past Simple
The dog was in the yard.
Was the dog in the yard? Yes,it was/No,it wasn't.
The dog was not in the yard.
Future Simple
The dog will be in the yard.
Will the dog be in the yard? Yes,it will/No,it won't.
The dog will not be in the yard.
Present Simple
Mother is at work.
Is mother at work?Yes,she is./No,she isn't.
Mother isn't at work.
Past Simple
Mother was at work.
Was mother at work? Yes,she was./No,she wasn't.
Mother wasn't at work.
Future Simple
Mother will be at work.
Will mother be at work? Yes,she will./No,she won't.
Mother won't be at work.