To solve this question, the user needs to know about pointers in programming languages. A pointer is a variable that stores the memory address of another variable. The symbol used to declare a pointer variable is the asterisk symbol (*), thus option A is the correct answer.
Option A: * is the correct symbol to declare a pointer variable.
Option B: - is not used to declare a pointer variable.
Option C: + is not used to declare a pointer variable.
Option D: | is not used to declare a pointer variable.