Luke Gave Some People Street Directions, but Because They Only

Multiple Choice

Luke gave some people street directions, but because they only nodded their heads and didn't repeat the directions back to him, he doesn't really know whether the directions were understood. Why?

A) Because they did not respond, there may have been a feedback barrier.
B) Because they did not respond, there may have been a sender barrier.
C) Because they did not respond, there may have been an encoding barrier.
D) Because they did not respond, there may have been a medium barrier.
E) Because they did not respond, there may have been a decoding barrier.