I need help dont understand.

A is the only function.

If they list out the x’s (like in B and C) and they have two of the same x’s, it is not a function. If they have those circles (like in D) and one x goes to multiple y’s, then it is also not a function. Hope this helps!

I believe it’s A. Because each x only can have one y. Every other equation has two different y if the same x. (Sorry if it doesn’t make sense)

Ithink it is b and d