Final answer:
The sentence in question is a simple sentence as it contains one main clause with a subject and a predicate and can stand alone as a complete thought. The correct answer is a) Simple.
Step-by-step explanation:
The sentence "Olivia, my best friend, sits right next to me on the bus." is a simple sentence. Despite the additional information that "Olivia" is the speaker's best friend, which is a non-restrictive element set off by commas, the sentence still contains one main clause.
A main clause includes a subject and a predicate and can stand alone as a complete thought. In this case, the subject is "Olivia," and the predicate is "sits right next to me on the bus," making the sentence simple rather than complex, compound, or compound-complex.
It comprises of one main clause, which contains a subject (Olivia) and a predicate (sits right next to me on the bus). Despite the additional information provided by the appositive phrase "my best friend," the sentence still expresses a single complete thought and thus does not qualify as compound, complex, or compound-complex.