Which of the following statements is true?

a$.$ IFRS$/$ASPE requires companies to use cash$-$basis accounting.

b$.$ Accrual$-$basis accounting records both cash and noncash transactions when they occur.

c$.$ The key elements of accrual$-$basis accounting are the revenue recognition principle, the periodicity assumption, the matching concept, and the historical cost principle.

d$.$ Under cash$-$basis accounting, revenues are recorded when earned and expenses are recorded when incurred.