C. The author uses a simile to compare the feeling of nervousness to melting because the sentence uses the word "like," which is an underlying hint to similes. Without it, it would be a metaphor.
The downfall... then the resolution
Answer: No, his experiment is not designed correctly.
Explanation: He didn't use the same measurements in each experiment. He should've either buried them all in the yard, or she should've kept them all in pots. Not having them in the same environment could affect the results of his experiment, thus making it inaccurate.