单项选择题
A.java.lang.Throwable
B.javax.servlet.jsp.PageContext
C.javax.servlet.http.HttpServletRequest
D.javax.servlet.http.HttpSession
E.javax.servelet.jsp.JspPage
F.javax.servlet.ServletConfig
G.javax.servlet.ServletContext
H.javax.servlet.jsp.JspWriter
I.javax.servlet.http.HttpServletResponse