下列各措施可减小偶然误差的是()
A.校准砝码
B.进行空白试验
C.增加平行测定次数
D.进行对照试验
E.使用高纯度试剂
参考答案:C
Tom urged that he _____ with so much work while his parents went on a snorkeling trip. [ ]
A. was left alone
B. not be left alone
C. will be left alone
D. isn't left alone
在热带雨林中,______植物是附生关系的一种特殊类型。