Alejandro wants to explain the importance of file extensions to his friend.

Which of these explanations is the best?

Choose $1$ answer:

When a file has an extension, the user knows who created the file.

When a file has an extension, the computer can decide what application to open it in$.$

When a file has an extension, the computer knows exactly how much memory it needs to allocate for it$.$

When a file has an extension, users can open files in applications they don't own.

When a file has an extension, the computer is allowed to store additional metadata about it$.$