Which of the following pair of acronyms and their expansion is incorrectly…

Concept

An ICT acronym is not a free description. Its expansion is fixed word for word by the standard or specification that defines the technology, so replacing even one defined word with a near-synonym makes the pair wrong.

So the way to test a pair is documentary rather than intuitive: identify the body or document that defines the technology, take the expansion exactly as that document writes it, and compare it word by word with the pair on offer. A word that merely sounds plausible for a letter, such as plan, program or procedure for P, is acceptable only if the defining document itself uses it.

Application

Read each acronym letter by letter and compare it with the expansion its own defining document uses.

Three of the four pairs reproduce these expansions exactly. The pair "SMTP - Simple Mail Transfer Plan" puts Plan where the standard says Protocol, so that is the incorrectly matched pair and therefore the answer.

Cross-check

• Expand the letters of SMTP against RFC 5321, the document that defines internet mail transfer: Simple, Mail, Transfer, Protocol. The final word is Protocol, so "Plan" cannot be the standard expansion.

• The same test leaves the other three untouched: Subscriber Identity Module comes verbatim from the GSM/3GPP specifications, Structured Query Language from ISO/IEC 9075, and Uniform Resource Locator from RFC 1738.

• Note that the question asks for the pair that is incorrectly matched, so the pair carrying the faulty expansion is what has to be selected, not a correctly matched one.