节肢动物的共同特征是:身体有很多 构成;体表有 ;足和触角 。
体节 外骨骼 分节
克服某些试剂不稳定引起的误差可以采用()
A.双试剂单波长一点法
B.双试剂两点法
C.双波长法
D.单试剂法
E.单波长法
I often doubt _____. [ ]
A. that the film 2012 is worth believing
B. if the film 2012 is worth believing
C. that the film 2012 is worth to believe
D. if the film 2012 is worth to believe