function address(){

    /*请在此补充代码*/

    var sf=document.getElementById("sf");

    var sq=document.getElementById("sq");

    var ssf=["北京市","天津市","河北省","河南省"];

    var ssq=["朝阳区","西城区","西青区","武清区","石家庄","邯郸市","郑州市","开封市"];

    var sq2=["西青区","武清区"];

    var sq4=["郑州市","开封市"];

        selectAdd(sf,ssf,ssf);

        selectAdd(sq,ssq,ssq);

}

function selectAdd(obj,name,value){

/*请在此补充代码*/

for(var i in name){

    obj.options.add(new Option(name[i],value[i]));

}

}

function linkage(){

/*请在此补充代码*/ 

    var sf=document.getElementById("sf");

var sq=document.getElementById("sq");

var f=sf.value;

if(f=="北京市"){

    var sf1=["朝阳区","西城区"];

    sq.options.length=0;

        selectAdd(sq,sf1,sf1);

}else if(f=="天津市"){

    var sf1=["西青区","武清区"];

    sq.options.length=0;

        selectAdd(sq,sf1,sf1);

}else if(f=="河北省"){

    var sf1=["石家庄","邯郸市"];

    sq.options.length=0;

        selectAdd(sq,sf1,sf1);

}else{

    var sf1=["郑州市","开封市"];

    sq.options.length=0;

        selectAdd(sq,sf1,sf1);

}

}