Answer:
Option C.
Step-by-step explanation:
People often put up barriers, is the right answer.
The poem "Mending Wall" was written by Robert Frost during his stay in England. In this poem, the poet asks "where it is we do not need the wall"? and the response he perceives is that "Great fences make excellent neighbors''. The poet was wondering why people ever build walls or barriers in their lives. Therefore, the most suitable answer will be option C.