Mastering C++: A Comprehensive Quiz Based on 'Thinking in C++'

The register specifier is used to suggest to the compiler to keep a local variable ina register if possible, meaning it can be accessed and modified faster.

Option A, static, specifies that the variable is globally accessible and remains in memory throughout the entire execution of the program.

Option B, volatile, specifies that the variable's value may change at any time and should always be accessed from memory.

Option C, auto, is the default specifier for local variables and does not suggest any specific storage location.

Overall, the register specifier is the most appropriate choice for optimizing the performance of a local variable.