Drainage

20 per cent

Step 1: The Indus is one of the world's largest rivers with a total length of 2,880 km. Step 2: However, the Indus Water Treaty (signed between India and Pakistan) restricts India's utilisation of the Indus waters. Step 3: As per this treaty, India can utilise only 4,195 million cubic metres, which amounts to only 20 per cent of the total discharge of the Indus. Step 4: The remaining 80 per cent flows into Pakistan. Step 5: Options A (30%), B (50%), and D (40%) are all incorrect figures not mentioned in the chapter.

About 50%

Step 1: The Godavari is the largest Peninsular river, rising in Nashik district of Maharashtra. Step 2: Its total drainage basin covers 3,12,812 sq. km. Step 3: The chapter clearly states that about 50% of its drainage basin lies in Maharashtra. Step 4: The remaining basin is shared by Madhya Pradesh, Karnataka, Odisha, and Andhra Pradesh. Step 5: Options of 30%, 40%, and 70% are all incorrect — 50% is the specific figure mentioned in the curriculum, which is why Godavari is closely associated with Maharashtra despite flowing through multiple states.

Tsang Po – Tibet; Dihang – Arunachal Pradesh

Step 1: The Brahmaputra originates from the Chemayungdung Glacier, south-east of Manasarowar Lake. Step 2: In Tibet, the river flows parallel to the Himalayas and is called Tsang Po. Step 3: It takes a southward turn near Namcha Barwa and enters Arunachal Pradesh as Dihang. Step 4: In Bangladesh, the Brahmaputra is known as Jamuna, and it eventually merges with the Ganga (Padma) and forms the Meghna. Step 5: The first option reverses the correct name-region pairing, making it wrong. Options C and D incorrectly assign Jamuna and Meghna to wrong regions.

Brahmaputra

Step 1: Antecedent drainage refers to rivers that existed before mountain ranges were formed and continued to flow by cutting through rising mountains. Step 2: The Brahmaputra originates specifically from the Chemayungdung Glacier, located about 100 km south-east of Manasarowar Lake. Step 3: Like the Indus, the Brahmaputra is also described as an example of antecedent drainage. Step 4: The Ganga rises in the Garhwal Himalayas at the Gangotri glacier (Alaknanda and Bhagirathi), not from the Chemayungdung Glacier. Step 5: The Satluj originates from Rakas Lake, not Chemayungdung Glacier. Hence, B