In One Experiment, Pigeons Whose Clocks Were Shifted 6 Hours

In one experiment, pigeons whose clocks were shifted 6 hours flew in the wrong direction when they attempted to navigate by following their sun compass. What happened when another group of identically treated pigeons navigated on a cloudy day?

A) They used their polarized-light compass and flew in circles.
B) They were able to navigate by using their polarized-light compass.
C) They were able to navigate on the basis of olfactory cues.
D) They were able to navigate by using their magnetic compass.