Solution

The grammatical error of the sentence is in option D. There are two plurals for some nouns, each with a different meaning. ‘Index’ is one of them. It has ‘indexes’ and ‘indices’ as its plurals. ‘Indexes’ mean (in a book or set of books) an alphabetical list of names, subjects, etc. with reference to the pages on which they are mentioned’ while ‘indices’ mean ‘pointers on an instrument, showing a quantity, a position on a scale etc. There is no mention of topics of a book or something thus, “indexes” is wrong here. Thus, replace “indexes” with “indices” to make the sentence grammatically correct. Correct sentence: Poverty is compounded by inflation which has reached extreme levels in the region, as demonstrated by consumer price indices.