3 ways that classes can relate to each other...

[cmarcello]

Hello,
I am not understanding what a homework assignment is asking...
Name three ways that classes can relate to each other.

Would by Inheritance be one?
Or is this asking what different classes can share?

[pogrady]

They can inherit properties,
they can be friends and access member variables,
and they can be contained within another.

I can't think of any other way that classes can interact with each other.

[cmarcello]

Thank you.
I thought I was on the right track but was unsure.