Which word does the underlined clause modify?

Many ancient Egyptian tombs, * which were discovered centuries before*, had been robbed of their treasures.

A.

tombs

B.

ancient

C.

robbed

D.

Egyptian

Which word does the underlined clause modify? Many ancient Egyptian tombs, * which were discovered centuries before*, had been robbed of their treasures.

A.

tombs

B.

ancient

C.

robbed

D.

Egyptian

What were discovered centuries before?

Tombs, as it states in the passage.