丽丽有3 件上衣、2 条裤子，一共有□穿法。□内应填[ ]
A ．5 种
B ．3 种
C ．6 种
答案：C
These are your books. You must look after ______. [ ]
A. it
B. them
C. those
D. these
分离纯化后蛋白质含量测定常用( )
A．凯氏定氮法B．双缩脲法C．酚试剂法D．紫外分光光度法E．溴甲酚绿
