Hi warrior1991 - sorry for the slight delay.

Bottom line: The contest between option B and option C is not even close.
Option C wins.

People who are objecting to DUE TO are using a rule that does not exist.

Option B is a disaster.

Would you like to know what I really think?

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Let's strip this sentence just a little and diagram it.

Glacier and ice patch archaeologists face extreme challenges to find, document, and conserve artifacts when melting ice fails to keep them undetected, shielding them from decay due to changing climatic conditions, and safe from misappropriation.

• Original, slightly stripped:
Archaeologists face challenges to find, document, and conserve artifacts when melting ice fails to keep them undetected, shielding[?] them from decay due to changing climatic conditions, and safe [?] from misappropriation.

Archaeologists face challenges
-- to find,
-- [to] document, and
-- [to] conserve artifacts
WHEN melting ice fails to keep [artifacts]
-- undetected
-- shielding? them? from decay, and
-- safe from misappropriation

• Option B in the sentence

(B) Archaeologists face challenges to find, document, and conserve artifacts when melting ice fails to keep them undetected, shielding them from decay because of changing climatic conditions, and saving them from misappropriation.

(B) Archaeologists face challenges
-- to find,
-- [to] document, and
-- [to] conserve artifacts
WHEN melting ice fails to keep [artifacts]
-- undetected
-- shielding? them from decay because of [?] changing climatic conditions, and
-- saving them from misappropriation

• Parallelism

How could (B) possibly be parallel?
-- undetected is in the non-underlined portion of the prompt.
-- undetected and shielding are not parallel
-- undetected and saving are not parallel

It's not impossible for a sentence to contain both past and present participles, but if another option offers a past participle and a inoffensive adjective, why on earth would we choose this option B with TWO present participles? [quite aside from participial modifier errors and the incorrect "because of" ]

• modifier error

(B) has some weird stuff going on.
-- comma + present participle (verbING) modifies the preceding clause (or its subject, or the immediately preceding noun, although the last case is very rare)

-- in what way, at all, does shielding modify WHEN melting ice fails to keep [artifacts] undetected
Is shielding a contemporaneous event?
Ridiculous. The melting ice that is failing to cover the artifacts cannot also be shielding the artifacts.

Is shielding a result of when melting ice fails to keep artifacts undetected?
Ridiculous. Melting ice cannot both fail to keep artifacts covered and result in the shielding of those artifacts.
The artifacts are shielded because they are detectable? No. All kinds of wrong.

Does shielding modify the verb phrase "fail to keep?" Or the verb "fail"?
Does "shielding" tell us in what way the melting ice fails to keep the artifacts undetected?
(No. Artifacts that are shielded have no logical relation to artifacts that are now detectable.)
Is shielding connected to fail or fail to keep in any logical way? No.
The word shielding is the opposite of the verb to fail to keep [undetected].

How about saving? Saving cannot sensibly modify the clause WHEN melting ice fails to keep [artifacts] undetected.

WHEN melting ice fails to keep artifacts undetected, then the artifacts are VISIBLE
So . . . saving them from expropriation (being stolen) somehow fits with the fact that melting ice makes the artifacts visible?
Because the artifacts are visible, they are safe from being stolen?

Both shielding and saving are nonsensical.

Compare B, for example, to tthis official question, here (tropical bats), SPOILER ALERT

• BECAUSE OF and DUE TO? Stand by

• Option C is parallel and sensible

(C) Archaeologists face challenges to find, document, and conserve artifacts when melting ice fails to keep them undetected, shielded from decay due to changing climatic conditions, and safe from misappropriation.

(C) Archaeologists face challenges
-- to find,
-- [to] document, and
-- [to] conserve artifacts
WHEN melting ice fails to keep [artifacts]
-- undetected
-- shielded from decay due to changing climatic conditions, and
-- safe from misappropriation

Melting ice fails to keep artifacts:
(1) undetected;
(2) shielded from decay [that is CAUSED BY and due to climatic changes], and
(3) safe from expropriation.

All three of those adjectives are logical.
Modifiers? Undetected, shielded, and safe all refer to THEM, which in turn refers to artifacts. The modifiers are fine.

• DUE TO and BECAUSE OF

• because of is an adverb that should modify a verb. I don't see any verb that "because of" could be modifying.
-- we have plenty to eliminate B if we are not sure about because of.
Option B is neither parallel nor logical. Its participial modifiers, shielding and saving, are nonsensical.

One last issue: is DUE TO correct in option C? Yes.

There is no such rule as "due to must be preceded by a TO BE or linking verb."

Due to is an adjective. "Due to" is a weird adjective, I grant you that much. It's idiomatic.
But it's an adjective. It modifies a noun.
I can use DUE TO in two ways.

(1) I can put due to right next to the noun that it modifies, this way:
Inner city deterioration due to political and social neglect is appalling in a country this wealthy.
What caused the deterioration? Political and social neglect.

(2) I can place "due to" after a TO BE verb. (This construction is much more common but certainly not the only construction!)
Your good grades are due to your hard work.
(What caused your good grades? Your hard work.)

Substitute any one of the following three phrases in the sentence that contains DUE TO.
Does the sentence make sense? If so, then due to is correct.

• caused by
• resulting from
• attributable to

• Answer C is superior to answer B with respect to parallelism and modifiers: check DUE TO

Archaeologists face challenges to ... conserve artifacts
when melting ice fails to keep them undetected, shielded from decay due to changing climatic conditions, and safe from misappropriation.

. . . when melting ice fails to keep them . . . shielded from decay ATTRIBUTABLE TO changing climatic conditions, and safe from misappropriation.
. . . when melting ice fails to keep them . . . shielded from decay CAUSED BY changing climatic conditions, and safe from misappropriation.
. . . when melting ice fails to keep them . . . shielded from decay RESULTING FROM changing climatic conditions, and safe from misappropriation.

This is my first case scenario, the rarer of the two, in which DUE TO is placed right next to the noun it refers to.
Is decay attributable to, caused by, and resulting from changing climatic conditions? YEP.

DUE TO in this sentence has nothing to do with the previous clause and does not need a TO BE verb.

This contest between B and C is not even a close call.

C wins.

( warrior1991 , I really hope that this analysis helps, because this thread is kinda all over the place. Whew. )
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