Anushka Sharma ---------------- a defect in her nervous system

Correct sentence: Anushka Sharma was unable to feel pain because of a defect in her nervous system.

Explanation: The adjective "unable" is followed by the infinitive form, so "unable to feel" is the correct structure. "Because of" correctly introduces the cause (a defect in her nervous system).

Why the other wordings are incorrect:

• "was unable in feeling pain because of" is incorrect because 'unable' does not take 'in' + gerund. Use 'unable to feel' instead.

• "was disabled to feel pain in" is ungrammatical and incomplete: 'disabled to' is not a natural collocation and the trailing 'in' is misplaced. Prefer 'was unable to feel pain because of...'.

• "was incapacitated to feel pain because of" is not standard: 'incapacitated' is usually followed by 'from' or used without an infinitive. 'Was unable to feel' is clearer and idiomatic.

Note: Also ensure proper capitalization of names: "Anushka Sharma".