Find the part of the sentence that contains a grammatical error. If there is no error, select 'No error'.

The downturn in Malaysian rubber is severe (A) / on account falling rates, diminishing productivity (B) / of estates - small-scale ones (C) / in particular - and weak overseas demand (D) .

The correct answer is Option D: "in particular - and weak overseas demand".

To understand the error, we must first read the entire sentence as a connected whole:

"The downturn in Malaysian rubber is severe on account [of] falling rates, diminishing productivity of estates — small-scale ones in particular — and weak overseas demand."

Identifying the Error — Faulty Parallel Structure:

The sentence lists three causes of the downturn in a series connected by "and." Each item in this list should follow the same grammatical form (this is the rule of parallelism). Let's look at the three items in the list:

1. "falling rates" → uses a present participle (verb acting as adjective)
2. "diminishing productivity" → uses a present participle
3. "weak overseas demand" → uses a plain adjective

Items 1 and 2 both use the present participle (-ing) form to describe the nouns ("falling" rates, "diminishing" productivity). For the sentence to be grammatically parallel, the third item must also use a present participle.

Therefore, "weak overseas demand" should be written as "weakening overseas demand", so all three items share the same grammatical structure.

Corrected Sentence:

"The downturn in Malaysian rubber is severe on account of falling rates, diminishing productivity of estates — small-scale ones in particular — and weakening overseas demand."

The error lies in Part D, where the adjective "weak" breaks the parallel pattern established by the participles "falling" and "diminishing." Replacing "weak" with "weakening" corrects the grammatical inconsistency and makes the series perfectly parallel.