Could anyone help me to check whether what I wrote is natural and grammatically correct or not?

Thank you very much for your correction!!!!
1. These questions are used skilfully to give students a reason to read.
2. The second activity required students to check whether what they know about Marie Curie is correct or not and to find out the answers for what they want to know about her.
3. He gave pluses for pairs with good answers and didn’t set time limit for this task.
4. He spoke slowly, repeated the instructions several times, and used miming or hand signals when students didn’t understand.

Pairs - do you mean two people working together? "Partners" might be a better word choice.