Ace Your C++ Skills 2026 – Rock the ‘Thinking in C++’ Challenge!

Option A is incorrect because setting an environment variable would not specifically instruct make to use a certain makefile, but rather it would set a default makefile that make would use if a makefile is not specified.

Option C is incorrect because renaming the makefile to 'Makefile' would only work if the makefile was named something else to begin with. It would not allow for the use of a specific makefile.

Option D is incorrect because placing the makefile in the root directory would only work if the makefile was specifically named 'Makefile'. Otherwise, it would not be recognized as the makefile to be used.

The correct option, B, is the best choice because it directly allows for the instruction of using a specific makefile by specifying the file with the -f option. This option would work regardless of the name or location of the makefile.