Step 1: Understand the question:
We must pick the word that completes the sentence about who signs an outgoing letter.
Step 2: Recall the rule for signing letters:
An outgoing letter is a formal document of the organization. It is signed only by a person who has the authority to do so. This is called an authorised person.
The signature shows that the organization stands behind the letter.
Step 3: Check the options:
(1) Authorised: correct, because only a person given authority may sign.
(2) Senior: a person may be senior but still not have signing authority.
(3) Recognised: this word is not the term used for signing authority.
(4) Sanctioned: this refers to something approved, not to a person who signs.
Final Answer:
Every outgoing letter is signed by an authorised person, option (1).