You must be aware that traffic officers can immobilise your vehicle...

Why this is the correct answer

The correct answer is B. Spanish traffic law establishes a closed list of specific grounds on which officers may immobilise a vehicle. One of those grounds is when the vehicle exceeds the permitted levels of gases, smoke, or noise for its type. Option A is wrong because simply not carrying the original vehicle documents is not one of the listed grounds for immobilisation -- it may result in a fine, but the vehicle will not be immobilised for that reason alone (immobilisation applies when the vehicle lacks administrative authorisation to circulate, which is different from not having the papers on you). Option C is also wrong because immobilisation does not apply every time you receive a penalty; it only applies in the specific situations established by law, such as exceeding environmental limits, lacking insurance, refusing breathalyser tests, or dangerous vehicle defects.