Which word or group of words is represented by the word "period" in the term periodic table? a. group b. family c. energy level d. valence electrons

The correct answer is C : energy level.

As you can see in the image of the periodic table presented below, periods are the horizontal columns of the periodic table.
Elements belonging to the same period have the same electron shell, the same number of orbits filled with electrons.
Elements of the same period have similar chemical and physical characteristics