Which question is testable? a how does changing the amount of water affect the growth of corn? b is it ethical to use human tissue removed during surgery for scientific research? c are you happy with your new job? d will people be disappointed if car insurance rates increase?

C & D are only part of the question and unsuitable, so it's either A or B, but I'd say it's more likely A~ How does changing the amount of water affect the growth of corn? 

The main role of dna in the  cell is the long-term storage of information. it is often compared to a blueprint, since it contains the instructions to construct other components of the  cell, such as  proteins  and rna molecules.the main function of rna is to carry information of amino acid sequence from the genes to where  proteins  are assembled on  ribosomes  in the  cytoplasm. mark brainliest, my work is good.

Compound light microscope