When coupling a second trailer to a doubles combination, what should you do with the shut-off valves on the first trailer?

a.Close them

b.Open them

c.Leave them in the position they were already in

d.Remove them

Explanation

The shut-off valves on the rear of the first trailer must be open to allow air to flow through to the second trailer. Only the shut-off valves at the rear of the last trailer in the combination should be closed.

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About the CDL Exam

The CDL (Commercial Driver License) exam tests your knowledge of commercial driving rules, safety procedures, and vehicle operation. You must score 80% or higher to pass the written knowledge test. The exam covers general knowledge, air brakes, combination vehicles, and various endorsements.

This question is from the Double/Triple Endorsement Test #1 section. Practice with more questions from this category to build confidence before taking the official DMV test.

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