O erro está em dizer que o SOA DEVE desenvolver todas as funções, conforme diz o mini book Soa for dummies:
p. 37
Rather than trying to boil the ocean, the team picked out a few
critical business processes — pricing, discounting, configuration,
and ordering — to develop as enterprise-wide services. The idea
was to roll out individual services as pilots, obtain key wins with
targeted applications, and then start to make them generally
available to other parts of the business as reusable services.
Don’t try to boil the ocean. Don’t attempt to do everything
p. 55
at once. Initially, prove your success with SOA by starting
with a project that is small, achievable in a short time, and
will have a significant impact — then build incrementally.
A alternativa B) não está incorreta. Pra quem fala sobre chamar XML de protocolo, vejam o enunciado novamente:
(...) que através do uso do protocolo SOAP e XML, (...)
Se o enunciado tivesse se referindo a SOAP como protocolo. Se estivesse referindo-se a SOAP e XML teria escrito "dos protocolos". Seria como dizer:
(...) que através do uso do protocolo SOAP além de XML, (...)