Nearly 500,000 pupils are to be guinea pigs in a trial run of the new exams.新型考试将在近50万名学生中试行。

She was the first human guinea pig for the vaccine.她是这个疫苗的第一个人体实验者。

The doctor used himself as a human guinea pig to perfect the treatment.这位医生以自己为人体实验对象来完善治疗方法。