Which words in this sentence are an independent clause?
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.
a.
that had been hidden in a safe tomb, which had a clay sealing
b.
an american business person discovered a stockpile of king tut's items
c.
which had a clay sealing covering it
d.
that had been hidden in a safe tomb