If you put assert macros throughout your code, then

a. You have to put up with the resulting inefficiency and program halts with messages indecipherable to the user until you edit your code to remove them.
b. You can put #define NDEBUG in your code in the file just before the #include directive.
c. With most command line compilers and IDEs (integrated development environment), you can define NDEBUG for the compile session by using an IDE menu option or you can use the compiler command line option –DNDEBUG.

b) and c) are correct.
Explanation: a) is wrong. (And horribly pessimistic.) Easy options exist as pointed out in b) and c) to prevent the macros from being compiled into your code.