An open-circuited p-n junction has drift current flowing from the n-side to the p-side. The option A is false.

An open-circuited p-n junction has diffusion current flowing from the p-side to the n-side. The option B is true.

The diffusion current flowing from the n-side to the p-side if the junction is forward-biased, is false but the diffusion current (approx zero) flowing from the p-side to the n-side if the junction is reverse-biased, is true. Hence, the option C overall is false.

The diffusion current flowing from the p-side to the n-side if the junction is forward biased, is true but the diffusion current flowing from the n-side to the p-side if the junction is reverse-biased, is false. Hence the option D overall is false.

Therefore, the correct answer is Option B.