Which set of preprocessor directives is used to prevent multiple inclusions of header files?

Q

Which set of preprocessor directives is used
to prevent multiple inclusions of header files?
1 #ifndef, #define and #endif
2 #ifdefined and #enddefine
3 #define and #endif only
4 #$if and #endif
5 #if and #define

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A
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2012-04-30, 5203👍, 0💬