Sentence Correction

Archaeologists in Ireland believe that a recently discovered chalice, which dates from the eighth century, was probably buried to keep from being stolen by invaders.
(A) to keep from
(B) to keep it from
(C) to avoid
(D) in order that it would avoid
(E) in order to keep from


Please explain the solution for this .....OA [/spoiler]

"It" is needed to refer back to the chalice, D is awkward as chalice is avoiding something