Select the correct option to test your answer: A Complete decay of substance in 20 days B Complete decay of substance in 40 days C Decay of $$\frac{3}{4}$$ part of substance in 20 days D Decay of $$\frac{1}{4}$$ part of substance in 5 days Correct Answer: Option C (Decay of $$\frac{3}{4}$$ part of substance in 20 days) Verified correct option for Physics (Modern Physics).