What is the English word for "附件"?

李老师

What is the English word for "附件"?
A. Carbon copy
B. Per pro
C. Enclosure
D. Reference
      满分：6  分
2.  Which of the following is not included in the 'Style and Language' of a business letter?
A. Simplicity
B. Courtesy
C. Idioms and language
D. Length
      满分：6  分
3.  Which of the following choices is informal complimentary close of business letters?
A. faithfully yours
B. yours sincerely
C. yours truly
      满分：6  分