When is it necessary for a vehicle to undergo a Smog Check?

A Smog Check is required at specific times to ensure that vehicles meet California's emissions standards. This makes option B the correct choice. The Smog Check is mandated at key points such as when a vehicle is sold to a new owner, during the registration renewal process, and when a vehicle reaches certain age milestones, typically when it is over six years old. These measures are in place to reduce air pollution and maintain vehicle performance in compliance with state regulations.

The other options do not align with the requirements set forth by the California Bureau of Automotive Repair. The idea that the inspection is only necessary when the vehicle owner decides contradicts the legal framework established for emissions testing. Additionally, an annual inspection for every vehicle does not account for the exemptions and variations in testing frequency based on the vehicle's age and other factors. Finally, limiting the need for a Smog Check to instances of performance issues overlooks the broader purpose of the inspection, which includes environmental protections and regulatory compliance.