Correct!

You're riding a motorcycle on the road. What should you do before using your mobile phone?

Turn on the speaker phone function
Stop in a safe place
Correct answer
Slow down to 20 mph
Increase the separation distance to 4 seconds

DVSA theory test explanation

It's important that you're in full control at all times. Even using a hands-free phone kit can distract your attention from the road. If you need to use a mobile phone, stop in a safe place before making the call.