Gratuitous contract  is a contract in which one party only enjoys contractual rights without paying any price. In other words, one party to the contract gives a certain benefit to the other party, and the other party does not have to pay any price to obtain the benefit.
According to the above definition, which of the following options is not part of a gratuitous contract?
A lent his car to his colleague B for use, and signed an agreement with B, agreeing to lend it to him for one year, without paying the use fee, but it must be returned as scheduled