Read and classify. 请把下列单词归类。

my      three     pencil     board     her      red       his      your    four     

green   blue      eraser     seven     eight   paper    yellow

物主代词：                                                                                

学习用品：                                                                                

数字：                                                                                       

颜色：                                                                                       

从工程造价上看，一般四层、五层民用建筑的基础工程的造价约占总造价的（）。

A.10%～20%

B.20%～30%

C.30%～40%

D.40%～50%