My answer is
(A). It took me 01:49.
(A) In this version, "their deceptively simple designs embellished with ..." is an absolute phrase.
My issue with (A): "from artist to artist and region to region" should be "from artist to artist and
from region to region" or other constructs.
By scanning the other options, I see "their styles vary among artists and regions", which
might be better. But Keep (A) for now.
(B) At first glance, it contains Comma Splice Error.
If the sentence structure is supposed to be "X, Y, and Z", there should be a comma before "and their style is ...".
Even if the comma is added, X, Y and Z are not parallel in their meanings.
In addition, "their style" should be "their styles". The use of progressive verb tense is not justified.
(C) As in (A), it uses "from artist to artist and region to region".
The sentence structure indicates "X, Y, and Z" construct, but the first clause ("the Australian government has taken significant measures to preserve the art of the Aboriginal people") does not parallel in meaning with the second and third clause.
The second and third clause are more aligned with "whose paintings and sculptures are highly unique". After all, the antecedent for "their/they" is "whose paintings and sculptures". With such reasonable interpretation, however, the sentence fails to maintain parallelism.
(D) "their style varies among artists and regions" is a clause, which is not parallel with such phrase as "their deceptively simple designs embellished with rich and imaginative symbolism".
"their style" should be "their styles".
"with paintings and sculptures highly unique" is highly awkward.
(E) "their styles vary among artists and regions" is a clause, which is not parallel with such phrase as "their deceptively simple designs embellished with rich and imaginative symbolism".
The issue in (E) is more serious than that in (A).