From the definition of the function, each element in domain set has exactly one image in the rage set.
In relation 1, the elemnts e and x in domain set has more than one image in the range set. So, it is not a function
In relation 2, the element c in the domain set has mor ethan one image in the range set. So, it is not a function
In relation 3, every element in domain set has a unique image in range set.
So, it is a function.
In relation 4, the elemnt 3 in domain set has more than one image in range set. So, it is not a function