不溶性杂质
A．澄清度检奄法B．炽灼残渣检查法C．干燥失重测定法D．易炭化物检硷法E．溶液颜色检查法
以下杂质的检查方法是
参考答案：A
I ________ work out the problem at first, but after my teacher showed me an example, I ________ get the answer easily.
A．couldn’t; was able to
B．can’t; could
C．wasn’t able to; could
D．was able to; was able to
认真进行预防接种，预防小儿麻痹症的发生。向广大群众和医务人员说明小儿麻痹症的发生发展过程，以便尽早发现、及时治疗，预防疾病的发展而引起的残疾属于（）
A.一级预防
B.二级预防
C.三级预防
D.防截肢
E.防精神障碍
