Annual assessment question i got wrong?

Interested to see what others would answer to this

Question, After the issue of a VT20, the customer revisits the issuing VTS to ask for an amended VT20 as the VRM of the vehicle has been changed. The customer should be advised that this

A - can be altered by the VTS after the customer pays the fee on the Mot Fees and Appeals poster (VT9a)

B - can be altered by the VTS free of charge, providing the customer brings the vehicle and the amended V5C document

C - cannot be altered by the VTS, and they should be advised to contact the Driver and Vehicle Standards Agency (DVSA)

D - cannot be altered by the VTS, and they should be advised to contact the Driver and Vehicle Licensing Agency (DVLA)