Which is the subordinate clause in the sentence?

Some additional clues were found when a small pit, with linen bags and broken pottery, was discovered in 1907.

Asome additional clues were found
Bsome additional clues discovered in 1907
Cwith linen bags and broken pottery
Dwhen a small pit, with linen bags and broken pottery, was discovered in 1907

ღ C?

Verified Answer :

The correct answer is D, because that is the dependent clause in this sentence. C cannot be correct because that is not a clause, that is, it doesn't have any verb in it, which makes it a phrase.