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
Answer:
water and oil don't mix
they form an emulsion
oil is less dense then water
Explanation:
Since there are no given answers, let's examine all pieces of information we can find here.
After mixing two liquids, Janet shook this mixture. She did it in order to enhance the rate of dissolving. After some time passed, we see that these liquids are separated into two distinct layers, meaning that water and oil do not mix (oil doesn't dissolve in water). This also means that water and oil form an emulsion - an unmixable suspension of two liquids.
Another feature we can observe is that the oil had risen to the top. Denser liquid will always fall down, meaning that oil is less dense then water.
