Which plural spelling rule should you follow to make story plural?

recent brain research has shown some surprising benefits as a result of formal musical training. learning to play a musical instrument appears to develop parts of the brain that can even influence academic results. the studies indicate that the earlier a child begins training, the more benefits there are. one such study showed that children who began musical studies before the age of seven had a more developed brain in the region where language production and auditory processing take place. scientists believe there is mounting evidence to show that early musical training can improve brain function.

explanation:

many battles and wars (such as the one at gettysburg), are commemorated by statues or monuments, with some areas preserved as monuments and national parks. do you think this contradicts the message of "grass"? in at least 200 words, explain your thinking and cite evidence from the poem to support your opinion.