【正确答案】Dear Professor Harrison,
On behalf of the organizing committee of the English singing test this year organized by the Students' Union of our university, I have the honor to invite you to our final competition in the Oval Auditorium of our university at 7:00 p. m. on Friday, January 16th.
You are sincerely invited to attend the singing contest as our distinguished guest and act as a judge. Would you please make a 5-minute speech to give us students encouragement and suggestions toward the end?
We look forward to a reply at your earliest convenience and we would be particularly honored by your distinguished presence at the contest.