What Happens to the Mass Number and the Atomic Number

What happens to the mass number and the atomic number of an element when it undergoes beta decay?

A) Neither the mass number nor the atomic number change.
B) The mass number decreases by 4 and the atomic number decreases by 2.
C) The mass number increases by 2 and the atomic number increases by 1.
D) The mass number does not change and the atomic number increases by 1.
E) The mass number does not change and the atomic number decreases by 2.