Which part or parts of the paragraph indicate that the government will enforce a particular environmental policy?

factories are entitled to tax credits if they adhere to pollution control levels stipulated by the concerned administrative body
they are allowed to function for an additional two hours per day during summers.
they are not allowed to employ children below the age of 18 as laborers
factories that emit higher amounts of pollution will be subject to penalties.

The last one.

Explanation:

You are after the enforcement of an environmental policy. Giving tax credits is a positive incentive. You want the government to act negatively to punish the bad guys.

The second one does not involve the environment.

Operation 2 extra hours during summer is fine, but it is not environmental -- not directly.

This is a social responsibility of government, not an environmental one. It is good to see. It wasn't always that way, but the environment is not the issue.

The last one is your answer. The government is prepared to act as a power that can punish wrong doers. And the environment is effected.