Could you pass me a pen, please?

Which sentence is more polite/formal?

Can he do a backflip?

I can help you with your project if you want.

You cannot borrow my book because I need it.

My parents could not wear normal clothes to school. They had to wear uniforms.

Chloe can't play the piano very well.

When I was 10 years old, I could run really fast.

When Tim was 16 years old, he ... run 100 metres in 11 seconds.

Nicole ... drive, but she hasn't got a car.

I was feeling sick yesterday. I ... eat anything all day.

'You look tired'. 'Yes, I ... sleep last night.'

I can't see you on Friday, but I ... meet you on Saturday morning.

She ... stand on her head, but she can't do it now.

Many animals ... see clearly in the dark.

That shelf is too high. I ... reach it.

He ... do his homework because he lost his workbook.

I learned to play the piano when I was 10 years old, but I ... only play one song.

100 years ago, most people ... travel abroad because it was too expensive.