Read the passage given below and answer the questions that follow (Q. Nos. 91 to 99), by selecting the correct/most appropriate options:

1. Kangri Karchok, the Kailash Purana of the Tibetans describes the sacred elephant-mouthed river or Langchen Khambab as a long and extensive river that rises from the 'lake unconquerable', the Tso Maphan or Manasarovar that flows from the mountainous regions of Tibet. According to this holy book, this cold river with its sands of gold, circles the holy Manasarovar seven times before taking its course to the west.

2. The Langchen Khambab flows down from the red coloured mountains of the Kanglung Kangri Glacier in the Trans-Himalayan region of Tibet, channelling its way through the earth forests of Tholing and Tsparang of the Gugi Kingdom. These earth forests are full of pillars formed by rocks that collectively appear like a forest from afar – an 'out of the world' landscape that was formed by geological movements of the earth and erosion by wind and water. The Khyunglung ruins also lies on the northern bank of the Sutlej river in this valley which was once known as the 'Garuda Valley'.

3. This mighty river then flows north-west for about 260 km before entering Himachal Pradesh through Shipki La cutting across the formidable Himalayan ranges of Zanskar, the Greater Himalaya and the Dhauladhar. Subsequently, the waters meander through the gigantic Kinnaur Kailash-Jorkanden Range at Reckong Peo creating the terrifying Sutlej gorge. Then it streams into Shimla, Kullu, Mandi and Bilaspur and is responsible for the rich cultivation of grapes, apples and apricots all along its banks. After its confluence with the River Spiti at Khab it is known as Sutlej.

4. It is 1,448 km in length, making it the longest among the five rivers of Punjab. Extensively used for irrigation, it is topographically divided into the Upper Sutlej Basin and Lower Sutlej Basin. It leaves the Himachal boundary to enter the plains of the Punjab at the Bhakra Dam, the second highest gravity dam and a major point of water supply and electricity generation for the North of India.

Which one of the following words is most similar in meaning to the word 'gigantic' as used in the passage (Para 4) ?