Explanation:

The correct answer is option B, a message.

Informal and written in a hurry:
- A message is typically informal and is often written in a hurry, as it is a quick way of communication.
- It is commonly used for conveying short and immediate information.

Complete format of a letter not followed:
- Unlike a formal letter, a message does not follow a complete format with salutations, addresses, and signatures.
- It is usually concise and to the point, without unnecessary formalities.

Differences between a notice and a message:
- A notice is a formal written or printed announcement that is displayed in a public place or sent to a group of people.
- It follows a specific format and is used to inform and give instructions about something important.
- On the other hand, a message can be written or spoken, and it is a direct communication between individuals.
- Messages are often used for personal or informal purposes, while notices are more official and public.

Examples of messages:
- Text messages: Short messages sent via mobile phones or other messaging applications.
- Email messages: Informal emails sent between friends or colleagues for quick communication.
- Instant messages: Real-time online chat messages exchanged between individuals.
- Voice messages: Recorded audio messages sent through various communication platforms.
- Social media messages: Informal messages sent through social media platforms like Facebook Messenger or WhatsApp.

In conclusion, a message is usually informal and written in a hurry, without following the complete format of a letter. It is a quick and direct way of communication, often used for personal or informal purposes.