I'm not working tomorrow, so I don't had to get up early.

Correct — B, 'so I don't had to.' After the auxiliary 'do/don't', the main verb must be in its base form, so it should read 'I don't have to'. The past form 'had' cannot follow 'don't', making segment (b) the error.

Why the others are wrong

• (a)
  I'm not working tomorrow, — Error-free — the present continuous is correctly used for a fixed future arrangement.
• (c)
  get up early. — Error-free — 'get up early' is the correct base-form phrase completing 'have to'.
• (d)
  No Error — There is an error — 'don't had' must be 'don't have' — so 'No Error' is not the answer.

This is an error-spotting item on auxiliary verbs — the negative auxiliary 'do not / don't' is always followed by the base form of the main verb, never a past or inflected form.

No directly related past PYQ was found.

• practice — not a real PYQ

  Spot the error: (a) She / (b) doesn't likes / (c) spicy food. / (d) No error

  • (a)She
  • (b)doesn't likes
  • (c)spicy food.
  • (d)No error
  Answer(b) doesn't likes — after 'doesn't' the verb must be the base form 'like'.
• practice — not a real PYQ

  Choose the correct option: We ___ finish the report today.

  • (a)don't had to
  • (b)don't has to
  • (c)don't have to
  • (d)doesn't have to
  Answer(c) don't have to — 'don't' is followed by the base form 'have'.