To perpetuate means making something continue indefinitely. To maintain means to cause or enable something to continue. Perpetuate and maintain are synonyms, and in this case, the sentence provided sets a context in which maintaining is the best option, as Monsanto is interested in maintaining the so-called "safety” of their products.
a) "when the doctors came, they said said she had died of heart disease--of joy that kills" the doctors assume that mrs. mallard, who had a heart condition, is shocked to see her husband alive & the joy of seeing him alive kills her
