Thewords of an essay prompt can usually be divided into three categories: contentwords, limiting words and task words. Please select from the followingstatements the correct definitions. 
A、Content words: Also referred to as the “key words,” these reveal the topic of the essay, that is, what the writer should write about.
B、Limiting words: Also known as “process words,” these provide instructions and tell the writer what to do. 
C、Task words: These provide focus and set the topical boundaries of the essay.