John and Bob enter into a contract for Bob to build a swimming pool for John at John$$s house. They agree that after the pool is built, an inspector hired by John will examine the work and that John will have to pay only after the inspector provides a certificate saying the work has been performed according to the building code. With regard to the duty of John to pay for the pool construction, the agreement as to the inspector and his approval is best described as:

Group of answer choices

A$.$ An implied$-$in$-$fact condition

B$.$ An implied$-$in$-$law condition

C$.$ A concurrent condition

D$.$ A condition precedent

E$.$ None of the above