Final answer:
The incorrect cue for downward facing dog is bending the elbows at 90 degrees; correct cues include engaging the quadriceps and pressing the heels into the mat.
Step-by-step explanation:
Among the cues provided for the downward facing dog position in yoga, the one that is not a teaching cue is c. bend the elbows at 90 degrees. The correct form for downward facing dog includes engaging the quadriceps, pressing the heels into the mat, and pulling the belly into the spine to support the back. The elbows should remain straight in this pose to ensure the arms are strong and the weight is evenly distributed between the hands and feet.