Question

Mark all the statements that are true.

Answer 1

B and D are the only true statements.

A function is a relation for which each value from the set of the first components of the ordered pairs is associated with exactly one value from the set of second components of the ordered pair. Alternatively, you can think of this as for each x, there is one and only one y. Clearly that is not the case here, but it is the equation of the vertical line $x = 3$.