Choose the appropriate modal verbs to complete the sentences.
1. Sir, don't you know that when flying you (have to/must) show you passport. 2. I(have to/must) be at the meeting at 6 p.m. so I can't join you for dinner. 3.there are many guests in the house, George will (have to/must) sleep on the sofa 4. People (have to/must) realize there are limits to what we can do.

1. Sir, don't you know that when flying you (must) show you passport. 2. I (must) be at the meeting at 6 p.m. so I can't join you for dinner. 3. There are many guests in the house, George will (have to) sleep on the sofa 4. People (must) realize there are limits to what we can do.