Concept:The past continuous tense (was/were + verb-ing) describes an action that was going on at a past time. Use "was" with a singular subject and "were" with a plural subject.Solution:"When you left the shop" shows a past time, so the verb must be past: "was" or "were", not "are" or "is".The subject "Kwadwo and Adwoa" is two people joined by "and", so it is plural.A plural subject takes "were".Correct sentence: "What were Kwadwo and Adwoa doing when you left the shop?"Answer:Option B (were)