Identify the correct word from the given options, which means the following-
A person carrying a message from one place to another.
(a)Postman
(b)Messenger
(c)Peon
(d)Bearer

Hint: Here, the given sentence looks for a particular which signifies a person who carries messages. So, before answering the question, one must be familiar with the other terms provided in the option and try to recall what each of them signifies.
Complete answer: A One Word Substitution question requires you to replace a sentence with a single word. In the question, there may be more than one option that seems to be correct but we have to differentiate the options to get the answer.
Now, let us analyze the given options: Option(a) ‘postman’ is an incorrect answer because postman is a person who carries or delivers letters to different areas or addresses. So, this option is not the correct answer.
Option(b) ‘messenger’ is the correct answer. Messenger refers to a person who carries messages from one person to another. Example- He got an important message from his messenger.
Option(c) ‘peon’ is an incorrect answer because peon is termed to a person who does small official chores in an office but is not involved in documental works or meetings or official works. He does not carry any messages or information to any person or officers. So it is not correct.
Option(d) ‘bearer’ is an incorrect answer because bearer is referred to a person who carries something or brings something. It is also referred to a person who pays the amount or bears the expense of something. Example- Rohit is the bearer of this cheque.
So, option C is the correct answer.

Note: Although two options seem to be correct, that is, messenger and bearer, still bearer does not refer to carry messages only but may refer to carry any expenses on themselves of any pain or object while messenger defines to the messages from one person to other through the person as a messenger.