Maximum speed limit for goods vehicles in motorways

Hello I've purchased the Highway Code book for my oral test I've noticed that there are 2 different answers given in the book concerning maximum speed for Goods Vehicles on motorways. There is a table in the book which clearly states that the maximum speed limit for "goods vehicles or articulated vehicles having a maximum gross weight" exceeding 3.5 tonnes or not, is 80km/h. But when working a test paper, the answer to this question is 70km\h.. So which answer is correct for the maximum speed limit for goods vehicles in motorways, 70km/h or 80km/h? Thanks.