Since products in the chemical industry have extremely brief shelf liv

Major issues tested by this question: Absolute phrases, parallel participles, and comma + which modifiers

If there seem to be two sentences "stuck together" and the options give various ways to connect the sentences;
-- and if neither the normal conjunctions nor a "which" modifier works properly as "glue";
-- and other options contain a strange-looking connector (or no connector), decide whether the latter might be an absolute phrase.

• Absolute phrases
-- often "tack on a second thought" or tie together the first and second parts of a sentence
-- modify the main clause in some fashion (Mnemonic: absolute phrases modify "absolutely everything")
-- almost always consist of a noun and a noun modifier.

In this question, the absolute phrase is essentially a long-second part of the sentence that
both summarizes the first part and explains the history of the first part.

The absolute phrase consists of the noun "trend" and participial modifiers.

Within the absolute phrase is a comparison signaled by the marker word "and."
The parts of speech before and after that AND must be parallel.

The comparison in this sentence is difficult. Usually we look at the right hand side of
a comparison marker word. In this case, we have "continuing," which does little to clarify what the left side should be
As I have written before, if I have a choice, I attack time-consuming parallelism LAST.

Split # 1: COMMA + WHICH
• comma + which must refer to its preceding noun or noun phrase and
cannot be used to refer to an entire clause
• very rarely, the noun modified by "which" is not immediately before "which." That rare pattern does not apply here.
Nothing that precedes which in A, B, or D qualifies as an antecedent

A: which incorrectly modifies nineteenth century and seems to refer to the trend
B: which incorrectly modifies either short span of time or, very generously, manufacturers
Which is intended to summarize the whole preceding sequence. Not correct.
D: same as option (B)

Eliminate A, B, and D

Split #2: parallel participles
• although not common, a sentence, clause, or phrase may contain
both a past and a present participle such as begun and continuing
Participles do not indicate tense.
• In this case, begun and continuing are both participles. Both are adjectivial modifiers of trend
• we know that "begun" is a participle because it has no subject and it anchors an absolute phrase

-- absolute phrases are described HERE, on GMAT Club and and in this article, HERE.

• PARALLELISM
-- AND in the absolute phrase signals that parallelism may be an issue
-- what descriptive word comes before "and"?
BEGUN, which is some kind of verb thing without a subject (i.e., a past participle). BEGUN modifies trend

BEGUN [BY the early manufacturers OF chemical products IN the nineteenth century]
-- that phrase is (1) an adjective describing trend, and (2) an addition of historical details that complement the first part of the sentence

TO MAINTAIN PARALLELISM
-- whatever comes before and after the word AND must be similar parts of speech
-- After the word AND, therefore, we need another participle (and participial phrase)
-- the structure must be identical or nearly identical—not kinda similar

D: begun . . . and it is continuing
NOT parallel

C: begun . . . and continuing
Parallel

Eliminate D.
(Options A and E, omitted above, also fail to maintain parallelism.)

The answer is