Photochemical smog consists of an excessive amount of $X$,in addition to aldehydes,ketones,peroxyacetyl nitrate $(PAN)$,and so forth. $X$ is

Which of the following is wrong with respect to our responsibility as a human being to protect our environment?

How are aldehydes produced in the atmosphere?

Match the items in Column-$I$ with the compounds in Column-$II$.

Column-$I$	Column-$II$
$(A)$ Acid rain	$(1)$ $CHCl_2-CHF_2$
$(B)$ Photochemical smog	$(2)$ $CO$
$(C)$ Combination with hemoglobin	$(3)$ $CO_2$
$(D)$ Depletion of ozone layer	$(4)$ $SO_2$
	$(5)$ Unsaturated hydrocarbons

Smog is caused by the presence of which of the following?

Determine whether the following statements are true or false:
$(1)$ The lowest region of the atmosphere where all living organisms,including humans,reside is called the troposphere.
$(2)$ The troposphere extends up to a distance of $25 \ km$ from sea level.
$(3)$ The region between $10 \ km$ and $50 \ km$ from sea level is called the stratosphere.
$(4)$ The ozone layer that protects living organisms is located in the troposphere.