How can human activity increase biological or mechanical weathering?

Correct answer: By excavating land and exposing roots or surfaces

The direct answer is A: excavation can expose roots, rock surfaces, and cracks, increasing weathering. Weathering happens when exposed rock is broken or chemically changed by water, air, temperature variation, ice, salts, or living organisms. Human activity changes the protective cover of land. The reasoning is: digging or construction removes soil and vegetation; fresh surfaces and cracks become exposed; water and air enter them; roots may grow into cracks and push against their sides; heating, cooling, and moisture act more strongly; weathering becomes more likely. Option A is correct because excavation and construction create or expose surfaces where biological and mechanical weathering can operate. Option B is wrong because humans cannot stop the Sun through ordinary land-use activity, and this has no connection with the process. Option C is wrong because excavation does not reduce gravity; gravity remains essentially the same and is not the stated cause here. Option D is wrong because making the sea solid is impossible in this context and is unrelated to weathering. A useful memory cue is: digging opens the rock, and exposure gives weathering agents access. Human actions do not create every weathering process, but they can make natural processes faster.