Correct answer: D.

The value of a cash-or-nothing binary call is:

$$Q e^{-rT} N(d_2)$$

Intuition

• $Q$ is the fixed cash payout if the option finishes in the money.
• $e^{-rT}$ discounts that future cash payment back to present value.
• $N(d_2)$ is the risk-neutral probability that the option expires in the money and pays out.

So the option value is essentially:

Present value of the payout × probability of receiving the payout

That is why the formula uses $N(d_2)$, not $N(d_1)$.