As Used in Defining the Modified Accrual Basis of Accounting

As used in defining the modified accrual basis of accounting, the term "available" means

A) received in cash.
B) will be received in person within 60 days after year-end.
C) collection in cash is reasonably assured.
D) collected within the current period or expected to be collected soon enough thereafter to be used to pay liabilities of the current period.