Identify the colloidal materials present in domestic sewage.

Which measures can be taken to control noise pollution?
$I-$ Use of sound-absorbent materials or mufflers in industries.
$II-$ Creating horn-free zones around hospitals and schools.
$III-$ Setting permissible sound levels for firecrackers and loud speakers.
$IV-$ Restricting the use of loudspeakers after a certain time.

Name an industry which can cause both air and thermal pollution as well as eutrophication.

$NO_x$ contributes to all,except

Identify $X$ and $Y$ from the figure representing an Electrostatic Precipitator:
$X-Y$

What is the consequence of a lake being saturated with organic waste?