Read the sentence. An American businessperson discovered a stockpile of King Tut's items that had been hidden in a safe tomb, which had a clay sealing covering it. Which best identifies the independent clause?
A. An American businessperson discovered a stockpile of King Tut's items
B. that had been hidden in a safe tomb, which had a clay sealing
C. which had a clay sealing covering it
D. that had been hidden in a safe tomb