When a Not-For-Profit Organization Uses the Deferred Contribution Method of Revenue

When a not-for-profit organization uses the deferred contribution method of revenue recognition and receives a donation restricted to the purchase of land, when should the donation be recognized as revenue?

A) When the cash is received.
B) When the land is purchased.
C) When the land is put into service by the organization.
D) It should not be recognized as revenue at all.