Aerugo, also known as verdigris, is the green "bloom"
visible on many copper items, and is produced, like iron rust, over the course of time by the exposure of the metal to the oxygen in the atmosphere.
(A)visible on many copper items, and is produced
(B)that is visible on many copper items, and which produces
(C)visible on many copper items, and produces
(D)that is visible on many copper items, and that produces
(E)which is visible on many copper items, and which is produced
Chop the unnecessary clauses:
Aerugo
, also known as verdigris, is the green "bloom" visible on many copper items, and is produced
, like iron rust, over the course of time by the exposure of the metal to the oxygen in the atmosphere.
Aerugo
is the green "bloom" visible on many copper items, and
is produced over the course of time by the exposure of the metal to the oxygen in the atmosphere.
Clauses like B, D, and E will change meaning.
C is not parallel.
A is best option.