1. The word ‘mighty’ refers to the immense strength, height and majesty of the Himavant. The next line proves that this is what is meant — “there’s no equal anywhere on earth” is a statement about scale and power, not about beauty or age.
2. (ii) emphasise a point. These are rhetorical questions: the poet already knows the answer and expects the reader to supply it. “Which other river can match her grace?” means no river can, and “what scriptures else to name with them?” means there are none. Options (i) and (iii) fail because the tone of the whole extract is confident, not doubtful — a hesitant poet does not write “there’s no equal anywhere on earth”. Option (iv) fails because genuine inquiry expects information back; the poet wants agreement, not an answer.
3. Because the Ganga gives constantly and asks for nothing. Her water irrigates the fields of the plain, supplies the towns along her banks, supports fishing and boat traffic, and is believed to purify those who bathe in her — and she does all of this for everyone alike, without choosing. Generosity is a moral quality, so by giving it to a river the poet does two things at once: he personifies her, and he makes the land itself seem benevolent rather than merely fertile.
4. Because a river in the plains moves the way a graceful person moves — smoothly, unhurriedly and without any abruptness. The Ganga does not fall or crash; she winds in long curves, spreads and glides, and keeps the same unbroken motion for hundreds of kilometres. The word also carries its second sense: grace as a blessing conferred. So the line describes both how the river looks and what she is believed to bestow. In one word the poet turns a body of water into a woman walking.
5. unmatched. The line before the blank decides it — “what scriptures else to name with them?” asks whether any other scripture can even be placed beside the Upanishads. That is a claim about uniqueness, not about quantity. Abundant would mean there is a great deal of wisdom in them, which is true but is not what this rhetorical question says.