The scientists who explained that the greenhouse effect and the Earth's atmosphere function in a similar way were ...... .

How is $SO_2$ an air pollutant?

The growth of fish gets inhibited,if the concentration of dissolved oxygen is below $X \ ppm$. The value of $X$ is

Fill in the blanks:
$(1)$ Deficiency of fluoride is responsible for ............. .
$(2)$ The upper limit of lead concentration in drinking water is ............. .
$(3)$ The maximum limit of nitrate in drinking water is ............. .
$(4)$ ............. and ............. chemicals act as poisons for the nervous system.

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 incorrect statement from the following is: