In income statement, gross profit is always equal to?

Yes Option C is the right answer.

C. Sales-Cost of goods sold

c) sales-cost of goods sold--------------------

Answer is Cbecause the formula of Cost of Goods Sold is Sale-Gross profit or we can compute GP by using Trading A/c Because COGS = Opening stock + purchases - Closing stock. 

So GP = SALES-COGS

Sale -  Cost of goods Sold................!!!

Answer is

C)Sales-cost of goods sold

Gross Profit =sales - cost of goods sold

C)  Sales - Cost of goods sold = Gross Profit 

Option C..... it is always equal to Sales - COGS

Option C, Sales - cost of goods sold.