Answer:
European nations staked claims on paper while tribes claimed the ground itself, but the border remained a work in progress, an imaginary line, until troops clashed and treaties settled the question.
In 1849, after the Mexican-American War, the United States sent teams of surveyors, soldiers and laborers to mark this new line in the desert, which sounded simple but proved difficult. The teams struggled as the Southwest seethed with conflict.
Explanation:
A—
This sentence pretty much sums up what the writer of the passage wants to talk about. The other ones do not fit with the sentence “water is one factor that is necessary for growth” and do not fit the idea of the passage, which is what factors affect plant growth.
