Question

question 20
when can you use a reserved lane?
only if your vehicle meets the requirements posted about that lane
when there is heavy traffic
only if your vehicle uses at least 30 miles to the gallon of gas.

Explanation:

Reserved lanes (like HOV or special - purpose lanes) have specific requirements (e.g., number of passengers, vehicle type, etc.) posted for their use. Heavy traffic doesn't give a general right to use a reserved lane, and the 30 - mpg requirement is not a standard general rule for all reserved lanes. So the correct option is the one about meeting the posted requirements.

Answer:

A. only if your vehicle meets the requirements posted about that lane