Custom events are used for child to parent communication where child cmp is used to fire or dispatch the event and parent cmp handles the event. So the right answer is A and C

A B

I can read :
A . The parent component can use a custom event to pass the data to the child component,
D . The parent component can use a public property to pass the data to the child component.

But Here
https://developer.salesforce.com/docs/component-library/documentation/en/lwc/lwc.create_javascript_methods
I can read :
To communicate down the containment hierarchy, owner and parent components can call JavaScript methods on child components.

https://github.com/kriasoft/react-starter-kit/issues/909
How to call child component method from parent

So it may be C ?

Pretty hard Question

Its A and C

I guess the answer should be A and C, since events are used to pass data from child to parent.