单选题 The factory supervisor______instructed the workers to clean the plant and make certain that all equipment was in good working order before the inspector's visit.
【正确答案】 D
【答案解析】解析：根据上下文语义，此处表示“监管员明确地指示工人们”，故应选择副词(D)explicitly(明确地)。(A)arguably意为“可论证地”，(B)invisibly意为“看不见地”，(C)forgetfully意为“健忘地”。