The important part of the White Emperor's question was not in 'Which of your students will lead the Human race', but in 'When you die'.
The White Emperor was not interested in using Chen Changsheng and Yu Ren to provoke Shang Xingzhou.
He had frankly, nakedly, revealed his bottom line to Shang Xingzhou.
If Shang Xingzhou insisted on killing the Demon Lord, then Shang Xingzhou would come away from today with heavy injuries, or perhaps not walk away at all.
This naturally led to the question of which of his students the Human race would be passed to.
Why had the White Emperor so confidently asked this question?
Shang Xingzhou understood. Everything arose from the still-unmentioned Madam Mu.
She had been standing high in the clouds the entire time with no intention of leaving.
No matter how one looked at it, the betrayed White Emperor could not possibly forgive Madam Mu.