Its C Their because their is the only option refering correctly to the sentence. Read the sentence out loud with option C and you will "C" that it is correct lol
Reviewing of your notes should be your primary concern, then refer to subtle differences?
For example, The school district is making it hard for students to eat poorly
Nelson Rolihlahla Mandela was a South African anti-apartheid revolutionary, politician, and philanthropist, who served as President of South Africa from 1994 to 1999.<span> </span>