In invitation letters, what should we use if the addressee is unknown?

【单选题】In invitation letters, what should we use if the addressee is unknown?

A、Dear Mr. Wang
B、Dear Professor Liu
C、Dear Sir/Madam
D、Dear Mary

When we write an invitation, what should we make clear?

A、The time.
B、The place.
C、The reason.
D、How to reply.

To write an invitation card, we need figure out what an invitation card should _____________

A、

consist

be made up

make up of

 consist of

【多选题】When we write an invitation, what should we make clear?

A、The time.
B、The place.
C、The reason.
D、How to reply.