Janet mixed water and olive oil in a bottle. She shook the bottle for several minutes, and then she let the mixture rest. After a few minutes, all of the oil had risen to the top of the water. What can Janet conclude?

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.