Possible answer:

The birds were not chirping because they had understood that grandmother was dead.

Explanation:

- In the story "Portrait of the Lady" by Khushwant Singh, the narrator describes how the old lady, who had been a kind and generous hostess to the birds in her garden, dies in her sleep one night.
- The next morning, when the narrator goes to the garden, he notices that the birds are silent and still, unlike their usual lively and noisy behavior. He wonders why they are not chirping, and then he realizes that they might have sensed the absence of their benefactor.
- The narrator reflects on the relationship between the lady and the birds, and how she had nurtured them with food, water, and shelter. He also notes how the lady had derived pleasure from their company and how the birds had reciprocated her affection with their songs.
- The narrator concludes that the birds were not chirping because they had understood that the lady was no longer there to greet them, to smile at them, and to feed them. They had lost not only a source of sustenance but also a friend and a patron.
- Therefore, the answer to the question is b. The birds were not chirping because they had understood that grandmother was dead. The other options, a and d, might be partially true but insufficient or speculative. We cannot assume that birds have emotions like sadness or grief, or that they can comprehend the concept of death in the same way as humans. However, we can observe their behavior and infer that they have responded to a change in their environment that affects their survival and their social bonds.

D is the correct answer