Pollution can be controlled by

Which one of the following pairs is not correctly matched?

Assertion : Methane,a component of greenhouse gases,contributes about $20$ percent to global warming.
Reason : The introduction of multi-point fuel injection engines in automobiles has decreased methane content in the exhausts.

The monitoring stations,established by $NEERI$,have reported that Kolkata and New Delhi have highest . . . . . . and . . . . . . in air respectively.

Contribution of individuals: Women of Garhwal/Himachal.

$A$ large number of fish suddenly die in a lake near a village. Which of the following could be the reason for this?
$(a)$ Excessive use of urea and phosphate fertilizers in nearby fields.
$(b)$ Spraying of $DDT$ in the entire area.
$(c)$ The lake water has turned green and murky.
$(d)$ The population of phytoplankton in the lake has decreased,reducing the photosynthetic capacity.
Which two of the above reasons are responsible?