Identify the true $(T)$ and false $(F)$ statements regarding the disease known as fluorosis:
$(1)$ Fluorosis weakens teeth and bones.
$(2)$ Fluorosis is caused by fluoride concentrations greater than $2 \ ppm$ $(2 \ mg/L)$.
$(3)$ Fluorosis causes neuromuscular disorders.
$(4)$ Fluoride deficiency causes fluorosis.

The smog known as London smog is .....

What do you mean by ozone hole? What are its consequences?

$A$ water sample has $ppm$ level concentration of the following metals: $Fe = 0.2$,$Mn = 0.05$,$Cu = 3.0$,$Zn = 5.0$. The metal that makes the water sample unsuitable for drinking is

Mention the main causes for water pollution.

Given below are two statements:
Statement $I$: Chlorofluorocarbons breakdown by radiation in the visible energy region and release chlorine gas in the atmosphere which then reacts with stratospheric ozone.
Statement $II$: Atmospheric ozone reacts with nitric oxide to give nitrogen and oxygen gases,which add to the atmosphere.
For the above statements choose the correct answer from the options given below :