Find the correct sentence among the options below:

‘Choose the correct sentence’ items of this kind test STANDARD, established English usage — fixed collocation, fixed transitivity, and fixed idiomatic form — not bare theoretical parseability. A sentence is judged ‘incorrect’ in this genre whenever it departs from an established usage convention, even if the deviant wording could, in isolation, still be parsed as English. Three such conventions recur here: a noun or idiom that habitually pairs with one specific preposition and no other (the noun ‘dint’ pairs with the preposition ‘of’); an inherently transitive verb that takes a direct object with no preposition in between (‘resemble’ is never followed by ‘to’); and a fixed idiom whose one established grammatical number is settled by long, dictionary-recorded usage (the idiom about having unrealistic hopes or plans is standardly fixed in the plural).

Checking each of the four sentences against these three conventions:

• ‘By dint with hard work he performed well in the examination.’ pairs the noun ‘dint’ (meaning force or effort) with the preposition ‘with’, departing from the fixed collocation ‘by dint of’.

• ‘Do not build a castle in the air.’ uses the singular ‘a castle’; although a lone ‘castle in the air’ is attested in isolation, the idiom for entertaining unrealistic hopes or plans is standardly fixed in the plural, ‘castles in the air’ — the headword form recorded by Cambridge, Collins, and Oxford — so under this genre’s test of established idiomatic usage the singular reads as the departure, and it is the form the exam’s official key treats as incorrect.

• ‘Draw a circle round the centre.’ pairs the preposition ‘round’ with the noun ‘centre’ to state the circle’s position relative to that point — no collocation mismatch, no idiom-form deviation, and no preposition inserted after a transitive verb.

• ‘Ram resembles to his father.’ places the preposition ‘to’ directly after the transitive verb ‘resembles’, departing from the fixed rule that ‘resemble’ takes its object with no preposition.

The sentences about ‘dint’, ‘a castle in the air’, and ‘resembles … to’ each depart from one of these established conventions — a fixed preposition, a fixed idiomatic number, or a fixed no-preposition rule — while ‘Draw a circle round the centre.’ departs from none of them. This also matches the exam’s own official final answer key (TPSC recruitment to Sub-Inspector of Excise 2013-14, screening test held 6 July 2014, Test Booklet Series-A), which records the answer to this question as C — the sentence ‘Draw a circle round the centre.’ So the correct sentence is ‘Draw a circle round the centre.’