What will warn you of congestion in Tunnel?

Driving Theory test question
You are going through a long tunnel. What will warn you of congestion or an incident ahead?
A) Hazard warning lines
C) Variable message signs
B) Other drivers flashing their lights
D) Areas marked with hatch markings

Answer: C
Explanation:
Follow the instructions given by the signs or by tunnel officials. In congested tunnels a minor incident can soon turn into a major one with serious or even fatal results.