Features like rock ledges in badlands or rock fins standing above adjacent valleys are all examples of 1) chemical weathering 2) differential weathering 3) glacial erosion 4) river erosion

2) differential weathering

Explanation:

Weathering is the breakdown of rocks, soil and minerals, as well as artificial materials through contact with the atmosphere, biota and Earth's waters. Weathering occurs in situ, more or less as: "no movement", and therefore should not be confused with erosion, which involves the movement of rocks and minerals by agents such as water, ice, snow, wind, waves and gravity and Then be transported and deposited elsewhere.

These phenomena develop on rocks that have a variable resistance to erosion and weathering, so that part of them is eliminated better than others. A typical example is the degradation of soft layers when they are arranged, among other harder ones, in a series of sedimentary rocks, other examples could be feautres like rock ledges in badlands or rock fins standing above adjacent valleys. The term can be applied to shapes of any size, from small-scale "corrosion" to the development of hills and valleys throughout a region, controlled by rock hardness.

answer; native americans who sometimes actively impeded railroad construction; physical obstacles like rivers and canyons, and