From the following sentences, which sentence contains a dependent clause?
- Before taking the exam, my nephew studied really hard.
- I heard something strange when downloading some movies last night.
- The operator directly input the data after knowing about the repaired system.
- That my father has worked as a network designer for five years is true
Is option (1) the correct answer?
I'm a beginner in English and I got confused a lot when it comes to identifying dependent clauses. I hope somebody can help. Thank you.