方程mx+3y=4x-1是关于x、y的二元一次方程，则m的取值范围为______．
根据题意，得m-4≠0，
即m≠4．
—Mary can't help you _______ the house. Why?
—Because she is busy _______ a hotel reservation. [ ]
A. to clean; making
B. cleaning; making
C. cleaning; to make
D. to clean; to make
刮刀有哪几种类型？显示剂的种类有哪些？
