Choose the part of a sentence that is grammatically incorrect

The correct answer is Option (4) → bridge the digital divide

Gerund after a preposition:

• A verb that comes directly after a preposition (by, of, for, without) takes the -ing form (gerund), not the base form.
• Here the preposition by (ending part 3) shows the means: how AI can be a change agent.
• So by bridge must be by bridging: "... how AI can be a powerful change agent by bridging the digital divide."
• Corrected: What has excited many in India is how AI can be a powerful change agent by bridging the digital divide.
  Example: You can improve your English by reading a newspaper every day.

Why the Other Options are Incorrect?

Option 1: What has excited many — Incorrect. "What has excited many" is a correct noun clause used as the subject, with the singular verb "has"; no error.

Option 2: in India is how AI can be a — Incorrect. The singular verb "is" agrees with the clause subject, and "how AI can be a" is correct; no error.

Option 3: powerful change agent by — Incorrect. "a powerful change agent by" is correct; the error lies in the verb form that follows "by".