If the tax on gasoline is increased to provide incentives to curb air pollution, then the tax serves as

A user fee.

Explanation:

These are general fees that are known to be paid by some countries indigenous occupants which tends to commence its reading from the first of January till the 31st of December. They particularly known to be renewable in most cases. User fees confer with a financing mechanism that has two main characteristics: payment is created at the purpose of service use and there's no risk sharing. User fees can entail any combination of drug costs, supply and medical material costs, entrance fees or consultation fees. they're typically obtained each visit to a health service provider, although in some cases follow-up visits for the identical episode of illness is covered by the initial payment.

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