( )可作为索赔的有效证据。
A．发包人的口头要求
B．承包人的合理建议
C．发包人的合理建议
D．双方签署的合同变更协议
参考答案：D
下列化学方程式①-④中书写错误的是（ ）
①在空气中点燃镁条：2Mg+O2═2MgO
②锌粒和稀盐酸反应制氢气：Zn+2HCl═ZnCl2+H2↑
③将主要成分为碳酸钙的贝壳投入稀盐酸：CaCO3+2HCl═CaCl2+CO2↑+H2O
④用稀盐酸除铁锈：FeO+2HCl═FeCl+H2O．
A．①④
B．③④
C．②③
D．①②
I've been told that our teacher has _____ the deadline for the composition by two days and we have to
hand it in tomorrow morning.[ ]
A. made
B. cut
C. advanced
D. suggested
