Rashtriya Ekta Diwas, or National Unity Day, is observed on 31 October as the birth anniversary of

The correct answer is B, Dr Sarvepalli Radhakrishnan, born on 5 September 1888. He was a philosopher and a teacher who became the first Vice President and the second President of India, and when his students wished to celebrate his birthday he asked that the day be kept for teachers instead. It has been observed as Teachers' Day ever since.

Option A, Dr Rajendra Prasad, was the first President of India, born on 3 December, and no national day is tied to his birth. Option C, Dr A. P. J. Abdul Kalam, was born on 15 October, which is observed as World Students' Day. Option D, Jawaharlal Nehru, was born on 14 November, which is observed in India as Children's Day. All three are Presidents or Prime Ministers, which is what makes the options look alike.

The correct answer is B. On 14 September 1949 the Constituent Assembly decided that Hindi written in the Devanagari script would be an official language of the Union, a decision that later became Article 343 of the Constitution, and that date is kept every year as Hindi Diwas.

Option A is the commonest mistake in the whole of general awareness. India has no national language; the Constitution speaks of official languages, and the Eighth Schedule lists the languages of the Union. Option C is wrong because the first Hindi newspaper, Udant Martand, appeared on 30 May 1826, a date observed as Hindi Journalism Day. Option D is wrong because Munshi Premchand was born on 31 July, which is marked as his own anniversary and not as Hindi Diwas.

The correct answer is A, Sir M. Visvesvaraya, born on 15 September 1861. He was the engineer behind the Krishna Raja Sagara dam and the flood protection works of Hyderabad, served as Diwan of Mysore and was given the Bharat Ratna in 1955. Engineers' Day is observed on his birth anniversary every year.

Option B, Homi J. Bhabha, was the physicist who founded India's atomic energy programme and is remembered as the father of the Indian nuclear programme. Option C, Vikram Sarabhai, was the physicist who founded the Indian space programme and after whom the space centre at Thiruvananthapuram is named. Option D, Satish Dhawan, headed ISRO after Sarabhai and gave his name to the launch centre at Sriharikota. All three are scientists rather than the engineer honoured on this day.

The correct answer is B, 16 September. The day, formally the International Day for the Preservation of the Ozone Layer, marks the signing of the Montreal Protocol on 16 September 1987, the agreement under which countries agreed to stop using chlorofluorocarbons and other substances that thin the ozone layer.

Option A, 5 September, is Teachers' Day in India. Option C, 16 October, is World Food Day, which marks the founding of the Food and Agriculture Organization in 1945, and the matching day of the month makes it the strongest distractor here. Option D, 5 June, is World Environment Day, which is about the environment as a whole and is set by the United Nations Environment Programme, not by the Montreal Protocol. Learning each of these four dates with the reason behind it is the only safe way to keep them apart in the examination hall.

The correct answer is A, 8 September. International Literacy Day was declared by UNESCO in 1966 and has been observed every year since to remind governments of the work left in teaching people to read and write. Each year the day is kept with a theme chosen by UNESCO.

Option B, 8 October, is Indian Air Force Day, which marks the raising of the force in 1932. Option C, 21 September, is the International Day of Peace, observed by the United Nations. Option D, 11 October, is the International Day of the Girl Child. The literacy day and the air force day share the date of the month, which is the confusion this question is built on. The reason behind the date is worth noting as well: the observance came from a UNESCO resolution and not from any single country's decision, which is why it is called international.