Answer:
c. variables, constants, and functions
Step-by-step explanation:
A predicate is the property that some object posses. Predicate calculus is a kind of logic that combines the categorical logic with propositional logic. The formal syntax of a predicate calculus contains 3 Terms which consist of:
1. Constants and Variables
2. Connectives
3. Quantifiers
But in arguments to predicates and functions, the terms can only be combination of variables, constants, and functions.