The teacher decided to pre-test some students to check the difficulty of the exam.

pre-test 是由前缀 pre-（表示"在...之前"）和名词 test（测试）组成的复合动词，字面意思是"预先测试"。pre-test 指在正式考试前进行的测试，目的是评估考试难度或学生水平。