Study the diagram and identify the people who can speak only one language.

In a three-set Venn diagram, a region that lies inside exactly one circle, with no overlap into any other circle, represents elements belonging to that single set alone. A region formed where two or three circles overlap represents elements shared between those sets, that is, people who fall into more than one category.

Here the three circles are English, Hindi, and Tamil. Region I lies only inside the English circle, region J lies only inside the Hindi circle, and region K lies only inside the Tamil circle, none of them touches another circle. So I, J, and K together cover everyone who speaks exactly one of the three languages, that is, K + J + I.

Checking the other combinations against the same rule:

• L + M + O are the pairwise-overlap regions (English-Hindi, English-Tamil, and Hindi-Tamil), so they represent people who speak exactly two languages, not one.

• K alone correctly identifies the Tamil-only speakers, but the diagram has more than one region where people speak only one language, so K by itself is incomplete.

• I alone correctly identifies the English-only speakers, but the diagram has more than one region where people speak only one language, so I by itself is incomplete.

Hence K + J + I correctly identifies everyone who speaks only one language.