Right or wrong, I assumed this ground, and now avow it. What does the phrase assumed this ground mean?

A: Forged an agreement
B: Formed an alliance
C: Made a supposition
D:Took this position

The great depression, which lasted throughout the 1930s in the united states, affected many people, and it had a devastating impact on an entire subset of the u. s. population. modernist writer john steinbeck wrote about the toll the depression took on these families, many of whom were forced to leave their farms and find other sources of income.