Directions: Write an invitation letter to a professor, inviting him to the English singing contest to be held this January. Some necessary details must be included. Do not sign your own name at the end of the letter, using "Li Ming" instead.

A. in addition
B. in other words
C. in a word
D. in summary

A. have adapted to a new set of moral standards
B. are longing for the return of the good old days
C. have realized the importance of material things
D. are awakened to the lowering of their moral standards