Which of the following statement is correct? Select one: a. According to the matching principle, expenditure on R\&D should be expensed at the same time when the R\&D project generates revenue. b. According to the FASB conceptual framework, equity describes transactions or events that affect a company during a period of time. c. Recording deferred revenue when the contract is signed and recognizing revenue later when the performance obligation is fulfilled is an example of conservatism. d. The criterion by which accounting information value can be judged is that of decision userfulness