Which methods from&#

Which methods from the String and StringBuffer classes modify the object on which they are called？（）  

• A、The charAt（） method of the String class.
• B、The toUpperCase（） method of the String class.
• C、The replace（） method of the String class.
• D、The reverse（） method of the StringBuffer class.
• E、The length（） method of the StringBuffer class.