换填法垫层的材料是哪些（）？
A．块石，石灰
B．砂石
C．矿渣，水泥
D．均质粘性土
E．土工合成材料
F．红土
参考答案：A, B, D, E
选择与画线部分意思相同或相近的选项。
They tried and in the end they won the game. [ ]
A. at first
B. at last
C. at the beginning
D. at once
怎样判别晶体二极管的极性？
