Answer:
B. act or move at high speed.
Explanation:
The term hasten is derived from the word <em>haste, </em>which means to make something happen quickly. The word hasten is a verb, extended from the word haste and added with the pattern of verb '-en.'
Therefore, hasten means to <em>act or move at high speed </em>or to be quick on doing something, or move fast.
Thus option B is correct.
The speaker is talking about the water. During winter, the water enters the cracks and freezes and expands. It breaks the stone and makes cracks and when the water melts the holes are bigger. What he is describing is mechanical weathering which is common in nature.