В8 Воткните в предложение подходящий по смыслу модальный глагол: must, mustnt,

В8
Воткните в предложение подходящий по смыслу модальный глагол: must, mustnt, have to, can, cant, may, should,shouldnt neednt, need и если сможете, то растолкуйте почему так, а не по другому.
1. When my sister was three year old, she ___ read.
2. Take an umbrella. It ___ rain.
3. You ___ stop smoking, its harmful for your lungs.
4. Our employees ___ sign this agreement.
5. She left the office an hour ago! She ___ be already here.
6. We have a dishwasher, so you ___ wash-up.
7. Some parrots ___ speak well.
8. You ___ read in the dark.