The major difference in applying the accrual concept in governmental fund accounting, as opposed to...

Governmental fund accounting uses the modified accrual basis of accounting. Under this basis, revenues are recognized when:

They are measurable (amount can be reasonably determined)

They are available (collectible within the current period or soon enough thereafter to pay current liabilities — typically within 60 days)

This is the key difference from full accrual accounting, which recognizes revenue when it is earned, regardless of when received.

Relevant References:

GASB Statement No. 33 – Accounting and Financial Reporting for Nonexchange Transactions

GASB Statement No. 34 – Fund Accounting and Modified Accrual Basis

GASB Codification Section 1600 – Fund Financial Reporting

Answer: C. recognized when they become measurable and available