If the critical shear stress of a channel is XC, then the average value of shear stress required to move the grain on the bank is A. 0.5 XC B. 0.75 TC C. XC D. 1.33 TC

The correct answer is C. XC.

The critical shear stress is the minimum shear stress required to initiate motion of a soil particle. The average value of shear stress required to move the grain on the bank is equal to the critical shear stress.

Option A is incorrect because it is half the critical shear stress. Option B is incorrect because it is three-quarters the critical shear stress. Option D is incorrect because it is 1.33 times the critical shear stress.