下列代码的功能是产生4位随机数并保存,在“______”处应填入()。Random rnd=new Random();int randNum=rnd.nextInt(8999)+1000;String randStr=String.valueOf(randNum);_________________
A. page.setAttribute("randStr",randStr);
B. request.setAttribute("randStr",randStr);
C. session.setAttribute("randStr",randStr);
D. application.setAttribute("randStr",randStr);