AB seems to be the correct answer.
https://developer.salesforce.com/docs/atlas.en-us.pages.meta/pages/pages_controller_methods.htm

A is correct. i think is another way of saying getter send the value from controller to VF page.
C is not correct. i think is a website typo mistake, All other website on this same question has this option -
A corresponding Setter method is required for each Getter method. -
which is the correct answer.

not really sure about my answer being B and D but I can briefly explain why A and C is wrong.
A -> we cant pass a value on a getter method. Getter methods return values from a controller
C-> C is also wrong. Setter methods pass user-specified values from page markup to a controller.
More details: https://developer.salesforce.com/docs/atlas.en-us.pages.meta/pages/pages_controller_methods.htm

A & B is answer