Choose the most appropriate verb to fill in the blank. Both the gover…

The correct answer is Option (2) → mitigate

Complete sentence: Both the government and the civil society must work together to mitigate the cause of pollution. Government and civil society working together against pollution are trying to reduce it, so "mitigate the cause of pollution" fits the sentence.

Word	Meaning	Example
(1) crystallise	To crystallise is to form crystals, or to make an idea clear and definite. Neither meaning fits fighting pollution.	The discussion helped to crystallise our plans.
(2) mitigate (answer)	To mitigate is to make something bad less severe or harmful.	Planting trees helps to mitigate the effects of heat in cities.
(3) expedite	To expedite is to speed something up. Speeding up the cause of pollution would make matters worse.	The officer promised to expedite the passport application.
(4) perpetrate	To perpetrate is to commit a crime or harmful act. It is the opposite of what the sentence wants.	The gang perpetrated a series of thefts.