When an Atom Loses an Alpha Particle

When an atom loses an alpha particle,

A) its atomic number decreases by 2 units and its mass number decreases by 4 units.
B) its atomic number increases by 1 unit but its mass number remains unchanged.
C) its mass number decreases by 1 unit but its atomic number remains unchanged.
D) neither its atomic number nor its mass number changes.
E) its atomic number increases by 2 units and its mass number increases by 4 units.