During a Power Failure,how Should the EMT Verify Adequate Ventilations

Multiple Choice

During a power failure,how should the EMT verify adequate ventilations are being administered to an unresponsive patient with a tracheostomy tube using a bag-valve mask?

A) Observe for improving skin color.
B) Ensure a good connection between the bag-valve mask and the tracheostomy tube.
C) Observe for chest rise and fall.
D) All of the above