【步筱昕】評論
A、B、D三项中的物品是用来做实验的物品。在文章第四段最后一句The researchers then measured levels of capsaicin, which is used in research to cause coughing and as a sign of how well the medicine are stopping coughs.可知Capsaicin（辣椒素）用来引起咳嗽和作为这些药物如何止咳的依据。