In problems 9 through 11, Select the best answer to complete the statement, and place the letter of the answer in the space provided.
If a light is to be controlled from three different locations, the following switches must be used:
a. two three-way and one four-way.
b. two four-way and one three-way.
c. three three-way.
d. two double-pole.
e. three single-pole.