Incorrect!

Why should you use your mirrors when you see a hazard ahead?

Because you'll need to accelerate out of danger
To assess how your actions will affect the traffic behind
Correct answer
Because you'll need to brake sharply and stop
To check what's happening on the road ahead
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DVSA theory test explanation

You should be constantly scanning the road for clues about what's going to happen next. Check your mirrors regularly, particularly as soon as you spot a hazard. What's happening behind may affect how you respond to hazards ahead.