Answer:
Sod is another name for grass, and it often looks silvery-white in the winter.
Step-by-step explanation:
Robert Louis Stevenson's poem "Winter-Time" talks about the cold snowing winter. Moreover, the poem described the winter scene as from one's childhood, from a child's perspective.
When Trent reads the poem, he would most probably have a problem understanding what the speaker means by the word "sod". "Sod" is a word generally used to mean grass, or a meadow, pasture, lawn, grassland, etc. So, if he knows that sod is another name for grass and that it usually appears silvery-white in winter, with the snow covering it, he will better understand the poem's meaning.
Thus, the correct answer is the first option.