Answer:
Therefore, the correct answer is: The clause is “who are not registered.” It is non-essential. It does require a comma. The clause is “to the back of the elective course line.” It is non-essential. It does require a comma.
Step-by-step explanation:
The relative clause in the sentence is "who are not registered." It is non-essential and requires a comma. The clause "to the back of the elective course line" is also non-essential and requires a comma.