Answer:
Messenger RNA (mRNA), molecule in cells that carries codes from the DNA in the nucleus to the sites of protein synthesis in the cytoplasm (the ribosomes).
The independent variable should be the plants you used.
Q1: The answer is seasonal changes.
Q3: The answer is sodium.
Q4: Not sure, sorry.
Q5: And then I think it is A for this one, but I am not sure.