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) .

Let's analyze the given sentence to identify any grammatical errors.

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

Analysis of Part (B):
The phrase "on account" is incorrect here. The correct prepositional phrase is "on account of" or "on account of the" when specifying reasons for something (in this case, "falling rates"). Without the preposition "of", the phrase is grammatically incomplete.

Therefore, the error lies in part (B).

The correct option corresponding to part (B) is B.