单选题 Because alcohol is a solvent, it is a component of many liquid medicines.
A. basic ingredient in making medicines
B. combination of things of different qualities
C. one of the parts that make up a whole
D. substance that helps to cure certain diseases

【正确答案】 C

【答案解析】basic ingredient in making medicines制药的基本成分；combination of things of different qualities不同性质物品的化合物；one of the parts that make up a whole组成整体的一部分；substance that helps to care certain diseases用于治疗某一疾病的物质。