Answer:
Social language.
Step-by-step explanation:
Social language is the language that we use in an informal setting, around people we are familiar with and at ease with. It allows the use of simple languages, be it slang or even some coded words that are already understandable by the others. It also does not necessarily require the people to be formal with each other, thus the language need not be in the formal setting.
On the other hand, an academic language is a formal language that is used among academicians and students among each other. There can be no casual approach as this is a professional atmosphere, thus the use of the formal form of communication.
So, when Sara used the word "Yo! What's up?" it is a casual and a form of slang words that cannot be used or addressed in a professional circumstance. Thus, the correct answer is social language.