Mehlich's cunninghamella plague method is used to test . . . . . . . .

Answer: Option B

Mehlich’s cunninghamella Plaque method is used to test Phosphorous.
In this method, the soil is mixed with the nutrient solution, a paste is made, spread uniformly in the well of a specially constructed clay dish, inoculated on the surface in the center of the paste, and allowed to incubate for a few days.