Answer:
1. The museum is free. You _________dont______ pay for the entrance
2. You have to wear a uniform at school. You ______musnt________ wear blue jeans
3. The speed limit is 90 km per hour. You _____musnt_______ drive faster.
4. You live in a very small place. You _______musnt____ clean it every day. Just clean it twice.
5. Your job is from Monday to Friday. You _____dont_______ come on weekends.
6. That river is extremely dangerous. You ______musnt______ swim in it.
I narrowed it down to B and D. Going to say D though
