Two players in Motion

[bigjohn]

7.2.7 Situation: The quarterback by voice command has signaled his teammates to assume a set position while he is standing upright behind the center. The quarterback steps forward and places his hands under the center to receive the snap: (a) at the instant the snap is made; or (b) which is made after he is motionless, but prior to one second having elapsed; or (c) which is made after he is motionless for one second; or (d) which is made after he is motionless for one second, but while he is stepping backward with one foot as the snap is made.
Ruling: In (a), it is illegal motion. In (b), it is an illegal shift. In (c), it is legal. In (d), it is legal unless a teammate is also in motion at the snap.

Is (d) illegal motion or illegal shift if a teammate is in motion??