给定servletA的代码片段如下所示:public void doPost(HttpServletRequestrequest,HttpServletResponse response) throwsServletException,IOException{String id="itcast";______________________}Servlet B与servlet A同在一个有效的会话范围内,当把请求转发给Servlet B后,使B能够获得“itcast”值,下划线处应填入( )。
A. request.getSession().setAttribute("ID",id);
B. request.getSession().getAttribute("ID",id);
C. request.getSession().setParameter("ID",id);
D. request.getSession().getParameter("ID",id);