Final answer:
The correct button to discount a line item by $50 is likely 'Deduct Amount,' as it implies subtracting a specific value from an item.
Step-by-step explanation:
The question is asking which button should be used to apply a $50 discount to a line item. In most financial or business software interfaces, to deduct a specific amount from an item, the appropriate action would be to use a button likely labeled as 'Deduct Amount' or an equivalent that suggests a specific value is being subtracted from the cost of a line item. Buttons labeled 'Apply Discount' might be more appropriate for percentage-based discounts, 'Discount Line' could also refer to a percentage-based discount or a generic discount action, and 'Reduce Total' could imply adjusting the entire invoice or bill's total.
To directly reduce the cost of an individual line item by a set dollar amount, such as $50, the 'Deduct Amount' button (Option C) would typically be the correct button to use.