Consider the following statements about ozone: (a) Ozone is poisonous gas. (b) Ozone shields the earth's surface from the infrared radiation from the sun. (c) Ozone is a product of UV radiations acting on oxygen molecule. (d) At the lower level of the earth's atmosphere, ozone performs most essential function. The correct statements are

Statement (a) is correct because ozone ($O_3$) is indeed a deadly poison. Statement (c) is correct because ozone at higher levels of the atmosphere is formed when high-energy UV radiation splits molecular oxygen ($O_2$) into free oxygen ($O$) atoms, which then combine with $O_2$ to form $O_3$ ($O_2 \xrightarrow{\text{UV}} O + O$ and $O + O_2 \rightarrow O_3$). Statement (b) is incorrect because ozone shields the earth from ultraviolet (UV) radiation, not infrared radiation. Statement (d) is incorrect because ozone performs its essential protective function at the higher levels of the atmosphere (stratosphere), whereas at the lower level (troposphere) it is a toxic pollutant. Therefore, only statements (a) and (c) are correct, making Option B the right choice.