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.  

the electromagnetic spectrum includes, from longest wavelength to shortest: radio waves, microwaves, infrared, optical, ultraviolet, x-rays, and gamma-rays.