Question

in which form of locomotion is friction the greatest impediment to moving?
swimming
flying
running
hopping

Explanation:

Friction in fluids (swimming) is due to viscosity. Air has lower viscosity than water. For running and hopping on solid - ground, friction is mainly static or kinetic friction between solid surfaces. But the resistance due to water's viscosity during swimming is relatively high compared to air resistance in flying and friction in running/hopping on solid surfaces.

Answer:

swimming