Header files often have the file extension _____ A. .H B. .HE C. .HEA D. .HEAD

The correct answer is A. .H.

Header files are files that contain declarations of functions, variables, and other data that are used by other programs. They are often used to provide a common interface for different programs that need to interact with each other.

The file extension .H is commonly used for header files in C and C++ programming languages. This is because the C and C++ compilers expect header files to have this extension.

The other options are incorrect because they are not commonly used file extensions for header files.