It should be 3! That is the only logical answer to the question...
Answer:
I'm thinking observation vs inference
Explanation:
she does her research about the situation and then comes up with an idea. the idea can be seen as an inference since at the end of the article it says "proving to be more impossible than not", which leads me to believe it's more of an observation vs inference situation.
C.75 of the cell's mass is water
Answer:
heat transfer in a fluid in which hot fluid rises and cold fluid sinks; setting up a cycle