The correct answer is indeed C. When people are doing ordinary things, such as eating or walking. the poem talks about the indifference that most people feel towards the suffering of others, that could be taken place "While someone else is eating or opening a window or just walking dully along".
I would say D, but only sure 90%.
The answer is A: sweetest. Of the many apples you have tasted, which type do you think is the sweetest?
To answer this question, the only thing we must do is to analyze the very definition of the two early processes involved in natural language acquisition:
Holophrastic stage:
it is the child's language acquisition stage where the acquiring of syntax is mostly done by utterances of single words.
Telegraphic stage:
it is the child's language acquisition stage where the infant start uttering multiple words in an early stage.
so, to answer the question, in natural language acquisition, single words serve as complete sentences in the:
1: Holophrastic stage