The image is asking why written words are a type of digital information. The answer is B: Written words can be translated into spoken words.
This is because digital information is a type of information that can be represented and stored in a digital format. This means that it can be represented using a series of discrete numbers. Written words can be translated into spoken words using a process called text-to-speech synthesis. This process involves converting each letter of the written word into a corresponding sound. This results in a digital representation of the spoken word, which can be stored and transmitted using digital devices and platforms.
The other two options are not correct. Written words are not made using a constant set of letters, as there are many different alphabets used around the world. Written words can also be used to describe any idea, not just spoken words.
Therefore, the correct answer is B: Written words can be translated into spoken words.