Then a teaspoon each of instant coffee and sugar _____.

The correct option is A Is taken
From the passage, we know that the action performed with instant coffee and sugar is 'taking'. Since we need to convert the active voice to passive, we must consider the rules for tense change. In this sentence, the tense of the verb 'take' is simple present. To change it to passive voice, we must change it to its past participle form 'is taken'. Therefore, the most appropriate answer is B) is taken. Option A) taken is also simple past tense but because it does not have 'is' preceding it, it is incorrect here. Option C) would have been taking is incorrect because it is in present perfect continuous conditional tense but there is no 'if' at the start of the sentence.