The first phase of possession must be done in 4 to 5 passes in order to quickly find an available player forward. Once this first phase is completed, it is important that the rest of the exercise is very fast. The one-touch pass from player B must be precise and placed just in front of B or C.
Rhythm is crucial in this exercise: the sequences must follow one another to create enthusiasm among your players and avoid boredom (knowing that some players may not touch the ball in certain sequences).
For your information, this is one of the exercises practiced by Pep Guardiola at Manchester City in August 2018.