Where should the shut-off valves be closed in a doubles or triples combination?

a.At the rear of the first trailer

b.At the rear of the last trailer only

c.At the rear of every trailer

d.At the front of the first trailer

Explanation

Shut-off valves must be closed at the rear of the last trailer in the combination. All other shut-off valves between trailers must be open to allow air to flow through the entire brake system.

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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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