The AAMVA Manual's Section 8 "Test Your Knowledge" review opens with a question asking drivers to explain a distinction. Which distinction is it?

AAMVA CDL Manual, Section 8 "Test Your Knowledge," Question 1, p.8-8-2

The manual itself signals which concept it considers most important to verify by listing it as the very first review question. That makes the bulkhead-versus-baffle distinction a high-value topic to have solid before sitting for the tanker endorsement knowledge test.