The correct answer is C. fair value.
Equity-settled share-based payment transactions are transactions in which the entity acquires goods or services by issuing equity instruments to the supplier of those goods or services. The fair value of the equity instruments issued is used to measure the goods or services received and the corresponding increase in equity.
The fair value of an equity instrument is the price that would be paid for the instrument in an arm’s-length transaction between knowledgeable, willing parties. The fair value of an equity instrument can be determined using a variety of methods, such as:
- The market price of the instrument, if available
- The price of a similar instrument, if available
- The present value of the expected future cash flows from the instrument
If the fair value of the equity instruments issued cannot be estimated reliably, the entity shall measure the goods or services received and the corresponding increase in equity at the cost of those instruments.
Amortized cost is the historical cost of an asset, adjusted for any subsequent amortization or impairment. Net book value is the historical cost of an asset, less any accumulated depreciation or amortization. Historical cost is the original cost of an asset, including any costs of acquisition and preparation for use.
In conclusion, the correct answer is C. fair value.