Which of the following is a correct pair of singular and plural?

The correct pair of singular and plural is: Axis:Axes

Explanation for each option:

☀ Reef:Reef: This is incorrect. The singular form of "Reef" is "Reef," and the plural form is also "Reefs."

☀ Mouse:Mouses: This is incorrect. The correct plural form of "Mouse" is "Mice."

☀ Axis:Axes: This is correct. The singular form of "Axis" is "Axis," and the plural form is "Axes."

☀ Piano:Pianoes: This is incorrect. The correct plural form of "Piano" is "Pianos."