What is the cause of the greenhouse effect?

Which of the following statement$(s)$ is (are) incorrect reason for eutrophication?
$A$. excess usage of fertilisers
$B$. excess usage of detergents
$C$. dense plant population in water bodies
$D$. lack of nutrients in water bodies that prevent plant growth
Choose the most appropriate answer from the options given below:

$BOD$ values (in $ppm$) for clean water $(A)$ and polluted water $(B)$ are expected respectively:

Among the gases $(a)-(e)$,the gases that cause greenhouse effect are
$(a) CO_2$; $(b) H_2O$; $(c) CFCs$; $(d) O_2$; $(e) O_3$

Petroleum is a source of energy that is:

What is the percentage contribution of $CO$ to the total atmospheric concentration due to forest fires?