A is the answer. You would need soil with different amounts- including no amount- to determine how the fertilizer affects the plants
Since you are measuring the height a ruler would be a good idea as well.
I think A is the answer its hard to explain but i hope this helped.
Protein
Proteins are the most versatile
macromolecules in living systems and they play important roles in essentially
all biological processes. Protein makes up the capsid of a virus. The infective
extracellular form of a virus known as a virion contains at
least one unique protein synthesized by specific genes in the nucleic acid of
that virus. In almost all viruses, at least one of these proteins forms a shell
(called a capsid) around the nucleic acid. Certain viruses also have other
proteins internal to the capsid. Some of these proteins act as enzymes during
the synthesis of viral nucleic acids.
