Which of the following statements is incorrect?

The correct answer is Option (4) → There is a cattle into the field.

Errors in the sentence:

• This sentence has three errors:
  • Cattle is a plural noun with no singular form, so it cannot take "a";
  • for the same reason it cannot take "is";
  • into shows movement, whereas the sentence describes position, which needs "in".
• Corrected: There are cattle in the field.
  Example: The cattle are grazing near the river.

Why the Other Options are Incorrect?

Option 1: The lion and the unicorn fought for the crown. — Incorrect.

• Correct use: this is a correct sentence, a line of a well-known nursery rhyme.
• The two subjects take the past tense "fought".

Option 2: Humpty Dumpty sat on a wall. — Incorrect. Correct use: this is a correct sentence, the opening line of the nursery rhyme.

Option 3: Here is the watch that you asked for. — Incorrect.

• Correct use: the singular "watch" agrees with is.
• "Ask for" is the right phrasal verb, so the sentence is correct.