Sentence improvement — choose the most appropriate idiom: replace the phrase 'by far' with the broader, summary expression 'by and large' to read, 'Although India is still by and large a poor country, it can become rich if its natural and human resources are fully utilised.'

Given sentence
Although India is still by far a poor country, it can become rich if its natural and human resources are fully utilised.

Concept/Approach
We are improving word choice/collocation. 'By far' is an intensifier meaning 'to a great degree', which does not match the concessive nuance here. The sentence wants an overall characterization — 'on the whole' — which is conveyed by the idiom by and large.

Option analysis
• by and large = 'on the whole; generally.' Fits after 'still' to mean 'still generally a poor country'.• 'few and far between' = rare/scarce; illogical here.• 'by and by' = soon/after a while; wrong meaning.• 'No improvement' keeps a less suitable intensifier.

Final Answer
by and large