Hey there!
Profit is the difference between money used and money earned. In our case, A is the number of cups of lemonades sold. This is a measure of how much money you earn because each one had a certain cost and the number of sales is a total of how many were sold.
C is the amount of money spend on supplies. This is basically money used.
D is the weather on the day of the sale, and this could be a correlated factor to some of the data, but it is not used to determine profit.
Therefore, the answer is D.
I hope this helps! Have a great day!