The best definition is:
D. Profit is the financial gain for business activity minus expenses.
Step-by-step explanation:
Profit is basically met by the two factors which are
-The expense met by the firm in producing the product
-The price it actually sold for in the market.
If the second factor is indeed bigger than the first, then there is profit.
Indeed, there must also be a consideration that the expenses would also include marketing, transportation and the cost for intermediaries.
It would not production cost but it would be the cost of getting the product to the consumer.