某患者在服用大剂量木通后，出现了头晕、恶心、呕吐、胸闷、尿闭、心悸等症状。尿常规及血生化检查均提示肾脏病变。经查，该药材断面黄色，呈蜘蛛网状，摩擦残余粗皮，有樟脑样臭，口尝味苦。病人中毒的主要物质可能是（）

A.齐墩果酸

B.常春藤皂苷元

C.木通皂苷

D.白桦脂醇

E.马兜铃酸

Speaker A: I think tourism is a great way of helping the economies of developing countries.
Speaker B: ().

A. Yes, I agree. I myself like nothing better than travel.

B. Maybe. Can you explain the advantage of developing tourism

C. Well, in my opinion, the governments of developing countries should create more job opportunities for their people.

D. Yes, it is. Without tourism, those countries would be much worse off.