Water seeping into gravel, freezing, expanding, and cracking rock is an example of what?
a. transportation of weathered material
b. physical weathering
c. erosion
d. chemical weathering

The best answer  is B - physical weathering.

Physical weathering is the geological process of rocks breaking apart  without changing  their chemical composition.

Many rock surfaces have small gaps and crevices on them. Water can freeze in these gaps and crevices  when it is cold. when the weather gets warmer, the frozen water melts. Over time, repeated freezing and thawing creates ice wedges which may cause rocks to break.

Pressure , warm temperatures and  ice can cause physical weathering  with time 

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jefferson hoped to establish trade with the native american people of the west and find a water route to the pacific. jefferson also was fascinated by the prospect of what could be learned about the geography of the west, the lives and languages of the native americans, the plants and animals, the soil, the rocks, the weather, and how they differed from those in the east.

industry had made the u.s. the richest nation in the world at this time. the second industrial revolution caused growth in industry and transportation, which allowed increased trade between nations.