单项选择题
A developer wants too use EL to invoke a function using S{my：bloof（“foof”）}. Which is always true？（）
A. The method invoked by this function must be statie.
B. The function class must implement the Function interface.
C. The expression is NOT a valid EL expression for invoking a function.
D. The function must be declared in a web.xml file using the
E. The function class must have a method with the signature：Void bloof （java.lang.Strings）