Read the following conversation and answer the question.

M: I want to make sure my son receives this letter. It has an important certificate in it.

W: You can send it either by certified mail or registered mail. If you only want to make sure it is received, send it by certified mail. It's less expensive.

M: OK. How about this package?

W: What's in it?

M: A watch.

W: You should insure it for the value of the watch, and send it by registered mail. It's more expensive, but it's the safest way.

Question: What is in the letter? 

- A valuable book.

- An important certificate.

- A beautiful postcard.


An important certificate.