What Is the Primary Function of a Builder in Laundry

What is the primary function of a builder in laundry detergents?

A) To act as an emulsifying agent
B) To remove grease and other nonpolar stains
C) To remove hard water ions such as Mg²⁺ and Ca²⁺
D) To increase the tensile strength of a fabric
E) To accelerate the natural biodegradation process of a surfactant