Adjective Clause Basics Check

Is this correct: The students which left the room are looking for you.

• Yes, it's correct.
• No, it is NOT correct.

Should we use commas in this: Peru, which is a large country, is in South America.

• Yes, keep the commas.
• No, delete the commas

How many sisters do I have: My sister, who lives in Washington, is funny.

• one
• two or more

Is this correct: Cypress College that is my favorite college has a lot of new buildings.

• Yes, it's correct.
• No, there's a problem.

Is this correct: The drama students that took this class last semester.

• Yes, it's correct!
• No, there's a problem.

I understand the basics of adjective clauses.

• YES!
• It's still a bit fuzzy (unclear).