Which of the following is responsible for depletion of ozone in upper strato of the atmosphere-

Which substance is used to extinguish fire in substances like oil, fat and petrol?

Which substance is added in chloroform before the use of it as anaesthetic?

How many $\mathrm{\sigma }$ and $\mathrm{\pi }$ bonds are present in the structure of D.D.T respectively?

In the following sequence of reactions, the gaseous species $\mathrm{A}\text{,} \mathrm{B}\text{,} \mathrm{D}\text{,} \mathrm{E}$, respectively, are