Is he a good sweemer? - Yes, he is.
Can he swim? - Yes, he can.
Is he swimming? - Yes, he is.
Does he swim in the river? - Yes, he does.
Is a river there? - Yes, it is.
Is it a river? - Yes, it is.
Are the men carrying large boxes? - Yes, they are.
Are the boxes large? - Yes, they are.
Are there boxes in the room? - Yes, they are.
Do the men carry large boxes? - No, they don't
Are there books in the boxes? - No, they aren't
Is there a computer in the box? - No it isn't.
Do the men use the computers? - No, they don't.
Is the sportsman running? - No, he isn't.
Are the sportsmen running in the park? - No they aren't.
Are there sportsmen in the park? - No, they aren't.
Does sportsman run? - No, he doesn't
Do sportsmen run? - No, they don't.