Let us go over the definitions and the functions of each term:
a) Gene is a bit vague but in general it means a part of DNA that encodes one protein. Genes are the building blocks of our genomes but not the answer to this question.
b)mRNA. This is correct. The name itself means messengerRNA and its role is to copy the genetic information in the nucleus and bring it outside to be translated into protein.
c) ATP is an important molecule in our metabolism; energy is stored in this molecule and then used. It has no relationship to the mechanisms concerning DNA.
d) Thymine is one of the 4 nucleotide bases that are found in DNA, the other three being guanine, cytosine and adenine. They are essential components of a nucleotide (building blocks of DNA and RNA) but again, they do not transfer information out of the nucleus.
Correct answer: A). The enzyme influences the speed of change from substrate to product
The enzymes are the biological catalyst that speed up the rate of chemical reactions by decreasing the activation energy of the reaction pathway.
They increase the speed of change of substrate to the product and it remains unchanged in the reaction. Hence, it can be used again and again.
Enzymes are highly specific in nature, only a specific substrate binds to the enzyme's active site. Hence, a particular enzyme is required to catalyze a reaction.
Sympathetic division and the parasympathetic division
I've checked all the options and I think that the right answer looks like this: Mollusks have highly developed olfactory receptors.