The Governor decides, on the opinion of the Election Commission — option 1.

The provision. Article 192 provides that if any question arises whether a member of a House of the Legislature of a State has become subject to any of the disqualifications in Article 191(1), the question shall be referred for the decision of the Governor, and his decision shall be final. Clause (2) then requires that before giving any decision the Governor shall obtain the opinion of the Election Commission and shall act according to such opinion.

Why the distinction is drawn this way. Defection is a matter of party discipline within the House, so the Tenth Schedule entrusts it to the presiding officer — which is exactly why the question excludes it and why option 2 is the intended trap. The other disqualifications turn on facts outside the House altogether, and the framers thought it right that they be settled by an authority outside it, with the Election Commission, an independent constitutional body, supplying the determining opinion so that the decision is not a political one.

The role of the courts. The High Court, option 4, does not decide such a question at first instance, though its writ jurisdiction under Article 226 remains available. The State Election Commission, option 3, is a different body altogether, created by Article 243K to conduct panchayat and municipal elections, and has no role here — the Commission whose opinion binds the Governor is the Election Commission of India.

Hence, the answer is the Governor.