The radius of the tank is , and the rate of filling the tank is .
Let the height of the cylindrical tank be h.
The volume of the tank is,
To find the rate of change of the volume, differentiate the above equation with respect to time.
The tank is being filled by wheat at the rate of . This is the rate of change of volume.
Hence, the depth is increasing at a rate of .
Thus, the correct option is (A).