Unless the conservator can find a way to protect the photographs in the archives from light and air, these precious historical documents have deteriorated and will continue to do so both in color and in fine detail.
A.
have deteriorated and will continue to do so
B.
win continue to deteriorate
C.
have been and will continue to deteriorate
D.
will continue to deteriorate, as they already have,
E.
will be deteriorating yet more