Final answer:
True. Stem-changing verbs keep their stem changes in the negative informal commands.
Step-by-step explanation:
True. Stem-changing verbs in Spanish do keep their stem changes in the negative informal commands.
For example, let's take the verb 'pensar' (to think):
In the affirmative informal command, which is used to give a command or instruction to someone you're familiar with, we say 'piensa' (think).
But in the negative informal command, we use 'no pienses' (don't think), where the stem change 'e' to 'ie' is maintained.