Final answer:
The word 'void' best matches the meaning of 'vacancy' as they both refer to an empty space or absence of something. 'Fullness' is the opposite, and 'potential' and 'opportunity' are unrelated to physical emptiness. Option b is the correct answer.
Step-by-step explanation:
The word "vacancy" refers to an empty space or position, similar to an emptiness that can be filled or occupied. Among the options given, "void" matches the meaning of vacancy best, as it also means an empty space or absence of something.
The other options do not represent emptiness; "fullness" is the opposite of vacancy, and "potential" and "opportunity" are not directly related to the concept of physical emptiness as vacancy or void would be.
So option b is the correct answer among the given option.