Помогите дополнить предложения следующими словами:
can, can't, mustn't, have to, don't have to, had to, didn't have to
1. When I was younger I could do gymnastics very well, but now I (...).
2. My sister (...) sing really well. She sings in a group.
3. You (...) wear special clothes to climb a mountain.
4. You (...) clean the car — I've done it.
5. I (...) forget my mum's birthday this year — last year I forgot!
6. We (...) walk up the stairs yesterday because Peter is afraid of lifts.
7. The school bus didn't arrive this morning but I (...) walk to school — my dad took me.