Only the towing vehicle of a semi-trailer unit is equipped with an anti-lock braking system (ABS). What could the effect of this be when performing an emergency braking manoeuvre on a wet carriageway?

Your answer is correct because when only the towing vehicle (the truck) has ABS and the trailer does not, the braking behavior can become unstable on wet roads. ABS on the truck helps prevent its wheels from locking, but since the trailer’s wheels lack ABS, they can lock and slide. This difference in braking control can cause the trailer to swing or jack-knife, increasing the stopping distance and reducing overall stability. Therefore, braking distance may be extended and the trailer may jack-knife, which is why both points 1 and 2 apply. Full ABS on both the truck and trailer is important to maintain stability during emergency braking.