Asubstance that enters into a chemical reaction is called a(n)
a. enzyme
b. reactant
c. catalyst
d. product

Option B

Explanation:

A reactant is a substance that take act as raw material for any chemical reaction.  

Catalyst is a substance that helps in either increasing or decreasing the rate of any chemical reaction without themselves physically taking part in any chemical reaction.

Enzyme is also a catalyst . It is in general a bio catalyst.  

The final substance produced in any chemical reaction is known as product.  

For example -  

Sugar(maltose) is converted into glucose in the presence of maltase enzyme

Here – sugar (maltose) is reactant

Glucose is product  

And maltase enzyme is catalyst.  

sorry, but you do not have posted the diagram.

"1. it should be, it has been for about 20 years, and it's really not much different in the end than breeding animals to have particular traits. there are always concerns about genetically engineered animals/plants affecting the environment in unexpected negative ways, but i can't think of an example where the fears didn't turn out to be baseless.  

first, as you point out, it would be a great advance in pharmacology, to be able to tailor drugs and their doses to me. the pros involve better medical treatment. the cons involve privacy issues like insurance companies denying coverage to people with genetic risk factors. looking at dna markers wouldn't affect the frequency of genetic diseases, but it would allow detection of them earlier. and ok, actually i suppose that if people used this information to avoid having children with genetic diseases, some might decrease in frequency."