选择题:5.The mayor promised to take effective measures to

题目内容:
5.
The mayor promised to take effective measures to ________ the city.
(A) agree on
(B) come to
(C) clean up
(D) pull out
参考答案:

3.设A为m×n矩阵,Aχ=0是非齐次线性方程组Aχ=β索对应的齐次线性方程组,则下列结论正确的是(

3.设A为m×n矩阵,Aχ=0是非齐次线性方程组Aχ=β索对应的齐次线性方程组,则下列结论正确的是()A.若Aχ=0仅有零解,则Aχ=β有唯一解B.若Aχ=0有

查看答案