设奇函数f(x)在上具有连续导数，则()
设二次型f(x1,x2)=x12+4x1x2+4x22经正交变换化为二次型，求ab的值。
Theenginehasbrokenandtheboatis______onthewater.
Thistest________anumberofmultiplechoicequestions.
Whenhesuddenly________upthesubjectofgeneticengineering,therewasanembarrassedsilence.
