First Principles Thinking: core idea
A is correct. The CFA Curriculum defines put-call parity as a no-arbitrage relationship among a put option, a call option, the underlying asset, and a risk-free asset. The governing relation uses the present value of the exercise price as the cash component. That is why the missing building block is the risk-free asset.
Why the other options are wrong: A dividend stream is excluded in this module because the underlying is assumed to have no income or benefit, and a swap payment is not part of the parity identity.