During the visual inspection, which statement about emission-control systems is NOT an expected requirement?

• A. They must be present.
• B. They must be intact.
• C. They must not be tampered with.
• D. They must be replaced with new units prior to testing.

Answer: (D)

The key idea is that the visual inspection checks the actual emission-control hardware that is installed on the vehicle. The system must be present, it must be in good, intact condition, and it must not be tampered with. Replacing the emission-control units with new ones before testing is not a standard requirement for the inspection. The test is about the current setup and its condition, not about pre-pass upgrades. Replacements would only be part of legitimate repair or replacement work, not a prerequisite for passing the visual check. The presence, integrity, and untampered state of the existing system are what the inspector verifies.