The Mason-Dixon line, which is perhaps the most famous border ever established by surveying methods, has been designated a National Historic Landmark. What are the two particilpes in this sentence?

1. The correct answer is C. The Mason - Dixon Line has been designed as a National Historic Civil Engineering Landmark. Main clause can also be referred to as independent clause. There is a verb and a subject in it and they express a thought which is complete.

2. Correct answer is C. Which is perhaps the most famous border which is ever established by surveying methods. Subordinate clause can also be known as dependent clause. It starts with relative pronoun and it has both verb and subject. A complete sentence can not be formed in this combination.

3. The correct answer is adjective. Subordinate clause functions the same way as adjective