During the late 19th and early 20th centuries, direct observations showed that a glacier in Switzerland flowed forward in the downhill direction while its snout (terminus) was retreating higher up the valley.
Which of the following explains these observations in a rational, scientific way?

A) Rocky debris in the valley downhill from the snout was deposited by Noahʹs flood.
B) Cooler temperatures meant slower forward glacier flow resulting in snout retreat.
C) The glacial hypothesis was finally accepted as a scientific theory.
D) The melting rate of ice in the glacier exceeded the rate at which new snow and ice were added to the glacier.