Under which Article of the Indian Constitution did the President give his assent to the ordinance on electoral reforms when it was sent back to him by the Union Cabinet without making any changes (in the year 2002)?

The correct answer is Article 123.

Article 123 of the Indian Constitution grants the President the power to promulgate ordinances when either House of Parliament is not in session. This legislative power allows the President to take immediate action if circumstances require it, provided the Union Cabinet advises such a move.

In 2002, when the Union Cabinet returned the ordinance on electoral reforms to President A.P.J. Abdul Kalam without any changes, he was constitutionally obligated to sign it under the framework of this Article, as the President generally acts on the aid and advice of the Council of Ministers.

For context, the other options are incorrect because Article 121 and 122 deal with restrictions on discussion in Parliament and courts not to inquire into proceedings of Parliament, while Article 124 pertains to the establishment and constitution of the Supreme Court.