补全短文
Pain is the most common reason we go to a doctor. It is the most common reason we take medicines. Until recently, however, most doctors knew of only a few drugs that stopped some pains. ________. But new knowledge about the process of pain is helping them to control pain better.
A、Yet we need pain.
B、They knew little about the process of pain itself.
C、And others have painful attacks all the time.
D、It is our body's Warning system.
【正确答案】 B
【答案解析】 空句所在的段落主要讲的是治疗疼痛的发展，许多医生只知道少量可以治疗一些疼痛的药物，这是由于缺乏对疼痛过程的认识。此处前后process也是对应词。
