The correct answer is (a) September 15.
Himalaya Diwas is a day to celebrate the beauty and importance of the Himalayas. It is celebrated on September 15 every year. The day was chosen to commemorate the first ascent of Mount Everest by Sir Edmund Hillary and Tenzing Norgay on May 29, 1953.
The Himalayas are a mountain range that runs along the northern border of India and Nepal. They are the highest mountain range in the world, and they are home to many different cultures and religions. The Himalayas are also a major source of water for many countries in Asia.
Himalaya Diwas is a day to celebrate the beauty and importance of the Himalayas. It is a day to learn about the history and culture of the Himalayas, and to appreciate the natural beauty of the mountains. It is also a day to raise awareness about the environmental challenges facing the Himalayas, and to take action to protect them.
The other options are incorrect because they are not the dates on which Himalaya Diwas is celebrated.