#define choice 3

#if choice == 3
....
#endif

#if choice == 4
...
#endif

macro is a rule or pattern that specifies how a certain input sequence (often a sequence of characters) should be mapped to an output sequence (also often a sequence of characters) according to a defined procedure. The mapping process that instantiates (transforms) a macro into a specific output sequence is known as macro expansion

An "if" statement is a control structure in many programming languages that changes the execution flow depending on a condition.