What are the answers to questions 17-21 about the poem?

Here are the answers to the questions based on the poem:

17. The poem is mainly about...
The poem describes the journey of trains over various terrains, what they carry, and their continuous operation. This best aligns with the overall movement of trains.
The correct option is B) the movement of trains.

18. The word 'freight' means...
In the context of "Thousands of freight cars," 'freight' refers to the goods or cargo transported by train.
The correct option is A) goods carried from one place to another.

19. 'Through dusk and dawn' means...
'Dusk' refers to the evening and 'dawn' refers to the morning. The phrase "Through day and darkness, Through dusk and dawn" implies that the trains operate continuously, covering all periods of time.
The correct option is D) all the time.

20. The word 'precious' means...
When the poem states "Bringing their precious loads," it implies that the loads are of great worth or value.
The correct option is A) valuable.

21. The mood of the poem is...
The poem uses positive language to describe the trains' powerful and continuous journey, carrying important items. It evokes a sense of admiration and wonder for the trains, suggesting an enjoyable or appreciative mood.
The correct option is D) enjoyable.