情态动词must与have to表义务 — 英语选择题
题目
根据昨天诊所的规定,Mia有义务出示预约单。哪句话表达了这个意思? A. Mia must show her appointment card yesterday. B. Mia had to show her appointment card yesterday. C. Mia didn't have to show her appointment card yesterday. D. Mia mustn't show her appointment card yesterday.