Which of the following is true of sustainability assurance?

	a.	It is the external verification that an independent party provides concerning the content of a corporate sustainability report.
	b.	The lack of a generally accepted set of reporting standards for preparing corporate sustainability reports leads to lower assurance costs.
	c.	Traditionally, most organizations have found it much easier to estimate the benefits of corporate sustainability reporting (CSR) assurance than the costs.
	d.	The cost of corporate sustainability reporting (CSR) assurance is always negligible.