The correct answer to this question is A, 6 feet. A person who works in HVAC and deals with housing codes would know the answer to this question. This is in correspondence with IRC G2408.3 (305.5). With all rules, there are exceptions. The exception to this rule is when vehicle impact is protected by appliances.
The appliances should also be installed with accordance to Section G2408.2. . These codes should not just be followed due to state laws, but they are put in place to protect the homeowner and their items from any damage. Before building a garage, the owner should learn the codes to ensure they are following the guidelines.