Gibberish is typically only used by young children. Not appropriate here since you're likely not talking about a 3-5 year old.
Formal language is typically only used in a professional setting or with people you're not familiar with (i.e. not your family or friends)
Jargon is like slang, but it's used in a professional setting. Doctors use jargon when talking about diseases. Ex: A "JT" is a joint. This isn't slang you'd use unless you were in their workplace.
It's slang because we use slang when talking to someone we're familiar with and in a non-formal situation. Borrowing a bike from our brother is non-formal, and we're familiar with him.
I believe the correct answer is B. Increases your reading speed. The reason for this is you are just shaming through what your reading to find the main idea, so you skip over the details that aren't that important.
When managers are strong communicators, they are better able to manage their teams. The delegations of tasks, conflict management, motivation and relationship building are all much easier when you are a strong communicator
