For each of the following variables, tell whether the various possible values may or may not overlap.
a. The variable is medication taken for blood pressure, and the possibilities include beta blockers, calcium channel blockers, diuretics, and ACE inhibitors.
b. The variable is gender.
c. The variable is instruments played by children in a gifted class, and the possibilities are piano, violin, flute, guitar, saxophone, other.
d. The variable is which candidate a voter plans to cast his or her ballot for, in a presidential election.