多项选择题
A Company.com developer chooses to avoid using SingleThreadModel but wants to ensure that data is updated in a thread-safe manner. Which two can support this design goal？（）
A. Store the data in a local variable. B. Store the data in an instance variable. C. Store the data in the HttpSession object. D. Store the data in the ServletContext object. E. Store the data in the ServletRequest object.
单项选择题 WhichHttpSessionmethodstoresanobjectinasession？（）
单项选择题 Whichelementistheparentofthetaginthewebapplicationdeploymentdescriptor？（）
单项选择题 Which retrieves the value associated with “foo” from within an HttpServlet？（）
