Here's why:
* Informal language is characterized by slang, contractions, colloquialisms, and a more casual tone.
* Personal emails to close friends are typically written in a relaxed and friendly manner, allowing for the use of informal language.
Let's look at other options:
* A formal essay for a college course: Formal essays require a more serious and academic tone, using formal language.
* A news report: News reports require objective and factual language.
* A job application letter: Job application letters require professional and formal language to make a good impression.
Therefore, writing a personal email to a close friend is the most likely situation where a writer would use informal language.