Is it true that carpets and curtains/drapes placed on the floor or wall surfaces can reduce noise level? Explain briefly.

Carbon monoxide $(CO)$ is a pollutant because...

Which of the following statements are correct regarding Eutrophication?
$I-$ Streams entering into a lake introduce nutrients like nitrogen and phosphorus,which encourage the growth of aquatic organisms.
$II-$ As the lake's fertility increases,plant and animal life flourish.
$III-$ Organic remains begin to deposit at the bottom of the lake.
$IV-$ Organic waste materials continue to accumulate in the lake.
$V -$ The lake becomes shallower and warmer.
$VI -$ Cold-water organisms are replaced by warm-water organisms.
$VII -$ Marsh plants take root in the shallows and begin to fill in the original lake basin.

Which of the following is not a pollutant?

Which of the following intensity of sound becomes a pollutant (in $\text{ dB}$)?

What is cultural eutrophication?