"Teacher, Du Xiu has passed the Senior Apprentice Examination."

Master Leng was slightly surprised, but remained calm, "Not bad, he didn't disappoint me."

When he discovered that poison powder at the Snow Forest camp, he knew Du Xiu had considerable skill in pharmacology.

Especially later, when he used poison powder to kill Zhou Yuan in the Snow Forest, Master Leng further guessed that Du Xiu had the level of a Senior Apprentice.