Select the most appropriate option to fill in the blank. John lost a large…

Coordinating conjunctions such as for, and, nor, but, or, yet, so (FANBOYS) each encode a distinct logical relationship between the clauses they join: reason (because/for), alternative (or), an added negative (nor, with inversion), and contrast (but/yet).

The first clause of this sentence states that John lost a large amount of money in gambling, an outcome that would normally be expected to reduce his standard of living. The second clause states the opposite: he still seems to live a lavish life. Joining these two ideas requires a conjunction that signals this unexpected, contrasting relationship between them.

• or would require the sentence to offer an alternative to the first clause (for example, 'either he stopped gambling or he lost his savings'), which this sentence does not present.

• because would require the second clause to give the reason the first clause happened, but living a lavish life is not the cause of losing money in gambling.

• nor requires the first clause to already be negative and calls for an inverted subject-verb order in the clause that follows (for example, 'he did not gamble, nor did he lose money'); neither condition is present here.

• but signals the contrast between the loss described in the first clause and the lavish lifestyle described in the second clause, which is exactly the relationship this sentence expresses.

Hence, 'but' is the conjunction that correctly joins the two clauses.