Read the passage given below and answer the questions that follow, by selecting the correct/ most appropriate options :

Each drop represents a little bit of creation and of life itself. When the monsoon brings to northern India the first rains of summer, the parched earth opens its pores and quenches its thirst with a hiss of ecstasy. After baking in the sun for the last few months, the land looks cracked, dusty and tired. Now, almost overnight, new grass springs up, there is renewal everywhere, and the damp earth releases a fragrance sweeter than any devised by man.

Water brings joy to earth, grass, leaf-bud, blossom, insect, bird, animal and the pounding heart of man. Small children run out of their homes to romp naked in the rain. Buffaloes, which have spent the summer listlessly around lakes gone dry, now plunge into a heaven of muddy water. Soon the lakes and rivers will overflow with the monsoon’s generosity. Trekking in the Himalayan foothills, I recently walked for kilometres without encountering habitation. I was just scolding myself for not having brought along a water-bottle, when I came across a patch of green on a rock face. I parted a curtain of tender maiden hair fern and discovered a tiny spring issuing from the rock-nectar for the thirsty traveller.

I stayed there for hours, watching the water descend, drop by drop, into a tiny casement in the rocks. Each drop reflected creation. That same spring, I later discovered, joined other springs to form a swift, tumbling stream, which went cascading down the hill into other streams until, in the plains, it became part of a river. And that river flowed into another mightier river that kilometres later emptied into the ocean. Be like water, taught Laotzu, philosopher and founder of Taoism. Soft and limpid, it finds its way through, over or under any obstacle. It does not quarrel; it simply moves on.

Which part of the following sentence contains an error ?
(a) He knew

(b) that he will

(c) go back

(d) on his promise