1. 
(-) this is not Marc
(?). is this Marc

2. (+) He is wearing a t-shirt and shorts today.
(-) Today he was not wearing a T-shirt and shorts.
(?) Is he wearing a t-shirt and shorts today?

3. He is eating an apple at the moment.
(-) He's not eating an apple at the moment
(?) . At the moment Is he eating an apple?

4. Marc likes fruits and vegetables.
(-) Marc doesn't like fruits and vegetables.
(?) Marc loves fruits and vegetables doesn't he?

5. He eats some every day.
(-) He eats a lot every day.
(?) He eats some every day, doesn't he.

6. Marc knows that apples are good for his health.
(-) Marc didn't know that apples were good for his health.
(?) Did Marc know that apples are good for his health?