我国自主研发生产的一种碳纤维产品，各项性能达到国际先进水平，其密度是钢的四分之一，强度是钢的十倍．它最不适合用于制作（  ）

已知a＝（1，2），b＝（3，－1）且a＋b与a－λb互相垂直，则实数的λ值为   （   ）

《共产党宣言》的诞生表明（   ）

     Tom and Mike are good friends. They are good with children. They want to find jobs in summer vacation. This Friday Tom tells Mike that Sunson School Trip needs teachers to help with sports, music and computer. Mike is glad to know that.
    Tom can play basketball, volleyball, and he can swim. Mike can play the violin, the trumpet, the drums and the guitar, and he can swim,too. Tom and Mike like computers very much. Can they join Sunson School Trip?

在加热时，浓硫酸与铜发生反应的化学方程式为：2H₂SO₄（浓）+Cu ​CuSO₄+SO₂↑+2H₂O对于该反应，下列说法中不正确的是（　　）