The equation given is \( y = 0.50x \), where \( y \) is the total cost and \( x \) is the number of apples.
To find the cost of just one apple, set \( x = 1 \):
\[ y = 0.50(1) = 0.50 \]
Therefore, the cost for 1 apple is $0.50.
So the correct response is: The cost for 1 apple is $0.50.