Answer:
My sister, who was the best student in her course, decided to work in a different area.
Explanation:
A relative clause is a clause or part of a sentence that helps define the 'who or what' in the sentence. A defining relative clause identifies the main noun or pronoun we are talking about. On the other hand, a non-defining relative clause provides additional information about the person or thing described.
In the given sentence, the subject is "my sister". By using the non-defining relative clause, we can join the two sentences by using a comma to separate the non-defining relative clause from the rest of the sentence.
Thus, the final sentence will be written as-
My sister, who was the best student in her course (non-defining relative clause), decided to work in a different area.
