The operation of vehicles is prohibited if:

Explanation

If at least one of the wheel bolts is missing.

There is no margin of tolerance on wheel bolts: the absence of even one bolt (or its being loose) prohibits operation of the vehicle. Highlight the phrase "at least one" in your mind, because it is usually this very phrase that makes the difference between the right and wrong answer in the exam.

The technical logic is simple: the force holding the wheel is distributed symmetrically across all the bolts. Removing one bolt makes the load on the remaining bolts both greater and asymmetric; with every revolution the wheel turns under a fluctuating stress on those few bolts, and the result is metal fatigue and the bolts failing in a chain. A wheel coming off in motion almost always ends in a total loss of control, and the loose wheel is itself a projectile for other vehicles.

The option about yellow indicators at the front is a trap. Yellow (amber) is precisely the standard colour for indicators; exactly what the regulations require. For this chapter keep a small colour table in mind: front white or yellow, rear red, indicators yellow/amber on both sides, reversing lights white, front reflectors white and rear reflectors red. Any option that fits this table is not an offence.

• Yellow or amber is the standard colour for indicators, so fitting them at the front is compliance with the regulations, not an offence; the option counts only on your mistaking "yellow" for a prohibited colour. • Since the first item is not a defect at all, the combined option is wrong too.

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