Why is the answer "B" instead of "A?"
Some historians believe that "the decline in wheat production was due to:"
1 Excessive irrigation
2 Lack of drainage
1 and #2 together lead to salt accumulation, problem #3
The way I understand it is that wheat production requires too much water, there isn't enough drainage, and salt builds up as a result of these two problems.
So with answer choice A, if barley requires less water than wheat, then does that strengthen the belief that they solved the too much water to produce problem (#1), the lack of drainage problem since less water needs to be drained (#2), and consequently salt accumulation is not a problem because the two problems causing it no longer are in the picture?
B, on the other hand, just accounts for salt buildup, but that is only a part of the problem because even if salt buildup doesn't matter anymore, we never accounted for too much water or the lack of irrigation.
Hopefully that makes sense and I appreciate any help.