Answer:
A. Section A
"Make audience laugh or smile"
You didn't underline anything, so we cannot know for sure what the correct answer is. However, I'll just write down the entire infinitive phrases in these sentences, and you can see the answer based on that:
1. to see a great play
2. to cheer good plays
3. to practice until you know all the plays
For the main reason that "it promoted sacrifice for the common good." the speech was commonly read during the Cultural Revolution. This speech was the primary political propaganda of Mao Zedong as a slogan during the dark times of the Chinese cultural history.
