Question

Select all the relations which are not functions. {(x, y) x is the date and y is the value of a stock at the close of the stock market that day}
{(x, y) x is the suggested retail price of particular car and y is price paid by a random car buyer for that car}
{(x, y) x is the price paid at checkout for one item and y is the item purchased}
{(x, y) x is a randomly selected child from an elementary school and y is the child's parent}
{(x, y) | x is a randomly selected natural number greater than 4 and y is the remainder when that number is divided by 4}