Which Is the Most Important Recognition Criteria Under IAS 18

Which is the most important recognition criteria under IAS 18 for revenue from services rendered?

A) The revenue amount can be reliably measured
B) The stage of completion of the transaction at the balance sheet date can be reliably measured
C) It is probable that the economic benefits from the transaction will flow to the providing entity
D) The costs incurred for both the transaction and implementing the services can be reliably considered