Though he is poor, but he is honest.

Correct — B, 'but he is'. 'Though' and 'but' are both contrast connectives, and standard English uses only one of the pair. With 'Though' already opening the clause, the 'but' in segment (b) is redundant; the sentence should read 'Though he is poor, he is honest.' The error is therefore in segment (b).

Why the others are wrong

• (a)
  Though he is poor, — A correctly formed concessive clause; the fault lies in the paired 'but', not here.
• (c)
  honest. — A correct subject complement completing 'he is'; not the error.
• (d)
  No error — The double connective 'Though … but' is a redundancy error, so the sentence is not error-free.

Error-spotting item on the 'Though … but' double-conjunction error — use only one contrast connective per clause pair.

No directly related past PYQ was found.

• practice — not a real PYQ

  Spot the error: 'Although (a) she was tired, / (b) but she / (c) finished the race. / (d) No error'

  • (a)she was tired,
  • (b)but she
  • (c)finished the race.
  • (d)No error
  Answer(b) but she — drop 'but'; 'Although' already marks the contrast.
• practice — not a real PYQ

  Which sentence is correct?

  • (a)Though it rained, but we played.
  • (b)Though it rained, we played.
  • (c)Though it rained, so we played.
  • (d)Though it rained, yet but we played.
  Answer(b) Though it rained, we played — one contrast connective is enough.