Take some anhydrous copper (II) sulphate powder and place it in a watch glass. Add water drop by drop to the anhydrous copper (II) sulphate. Do you notice any colour change in the powder? You can notice the powder turning blue. It is a test for water.

The value of \(\frac{cos^3 20° – cos^3 70°}{sin^3 70° – sin^3 20°}\) is  

A. 1/2 

B. 1/√2 

C. 1 

D.2