196. It is possible that Native Americans originally have migrated to the Western Hemisphere over a bridge of land that once existed between Siberia and Alaska.
(A)
have migrated to the Western Hemisphere over a bridge of land that once existed
(B)were migrating to the Western Hemisphere over a bridge of land that existed once
(C)
migrated over a bridge of land to the Western Hemisphere that once existed
(D)migrated to the Western Hemisphere over abridge of land that once existed
(E)
were migrating to the Western Hemisphere overa bridge of land existing once