On a white regulatory sign, a black symbol appears inside a red circle with a red slash running through it. What does this graphical construction communicate?

Why C is correct

The red circle with a diagonal slash is the universal grammar of prohibition: whatever the inner symbol depicts, that movement is forbidden here. The construction lets the sign system express an unlimited range of bans without new shapes — no left turn, no U-turn, no trucks, no parking — by keeping the frame constant and swapping the pictogram. Recognising the frame means you can read a sign you have never seen before, which is exactly what happens when you drive into a city with restrictions your home town has never needed.

Why the other options are wrong

A. The symbol marks the location of a traffic camera

Enforcement cameras carry their own markings and signage; the prohibition frame says nothing about how a rule is enforced, only that the depicted movement is not allowed.

B. The action shown is mandatory for all vehicles

A mandatory instruction is shown by the symbol alone in a red-bordered frame without a slash — speed limits are the classic case. The slash is what converts a symbol from something you must do into something you must not do.

D. The action shown by the symbol is prohibited

Time-limited permissions come from supplementary plates beneath the sign, not from the slash. The circle-and-slash construction itself is unconditional: it bans, whenever it is displayed.

On the road

Downtown for the first time in a rental car, you meet a white sign showing a truck inside the red circle and slash. You have never seen this exact sign before, but the frame is a language you already speak: no trucks through here. You route around the block rather than discovering the restriction from a citation in the mail.

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