A custom JSP tag must be able to support an arbitrary number of attributes whose names are unknown when the tag class is designed. Which two are true？ （）
- A A element in the echo tag LTD must have the value JSP
- B The echo tag handler must define the setAttribute （String key， String value） method
- C The true element must appear in the echo tag TLD
- D The class implementing the echo tag handler must implement the javax.sevlet.jsp.tagext.IterationTag interface
- E The class implementing the echo tag handler must implement the javax.sevlet.jsp.tagext.DynamicAttributes interface