True: if it is a function false: if it is not a function {(2, 3), (4, 5), (4, 3), (3, 4)}

false.

Explanation:

The given relation does not fit the definition of function.

A function is a relationship that states unambigously the image (output) of the input (independent) variable.

In the set of ordered pairs it is true form the input-values 2, and 3, because their images are 3 and 4, respectively.

But, could you tell the image of 4?. It may be 5 or 3. That is an ambiguity. That is why the given relationship is not a function.

A function is defined as a set of ordered pairs no two of which have the same first values or first component.

This means if more than one ordered pairs will have the same first component, the relation will not be a function. 

In the given relation, the first component of 2nd and 3rd ordered pair is the same, so the relation {(2, 3), (4, 5), (4, 3), (3, 4)} is not a function. 

So the Answer is False.