I would definitely say B.) A smile because if you were just staring it may be rude or distracting to the speaker and a smile shows you are listening and absorbing the knowledge
The theme is A birthday of my life
Answer:
1. dog
2. customers
3. barn
4. baby
5. yesterday
I believe these are the answers. English is one of my best subjects, but I don't really like analyzing sentences all that much, so it's hard for me sometimes :')