一个二次函数的图象的顶点坐标为(3,-1)与y轴的交点(0,-4)这个二次函数的解析式是( )
We have worked so long.Shall we stop ______ a rest?( )
A.haveB.to havingC.havingD.to have
Rules are helpful to us,______ we have to follow them.( )
A.soB.butC.orD.because
Tim is going to give his father a surprise ______ Father's Day.( )
A.inB.atC.onD.by
Ladies and gentlemen,attention please!I have ______ important to tell you.( )
A.nothingB.somethingC.everythingD.anything
I like hiking in the forest because the air is pretty ______.( )
A.freeB.dirtyC.pollutedD.fresh