-2的相反数是 ______，绝对值是 ______．
-2的相反数是2，绝对值是2，故答案为2，2．
能够对抗原或抗体进行定位的检测方法是（）
A.凝集试验
B.沉淀试验
C.中和试验
D.免疫组化试验
E.补体溶血试验
The course normally attracts 50 students per year,______up to half are from overseas.
A．in which
B．for whom
C．with which
D．of whom
