Increased use of incineration is sometimes advocated as a safe way to dispose of chemical waste. But opponents of incineration point to the 40 incidents involving unexpected releases of dangerous chemical agents that were reported just last year at two existing incinerators commissioned to destroy a quantity of chemical waste material. Since designs for proposed new incinerators include no additional means of preventing such releases, leaks will only become more prevalent if use of incineration increases. Which of the following, if true, most seriously weakens the argument? ['The capacity of existing incinerators is sufficient to allow for increased incineration of chemical waste without any need for new incinerators.', 'Other means of disposing of chemical waste, such as chemical neutralization processes, have not been proven safer than incineration.', 'The frequency of reports of unexpected releases of chemical agents at newly built incinerators is about the same as the frequency at older incinerators.', 'At the two incinerators at which leaks were reported, staff had had only cursory training on the proper procedures for incinerating chemical waste.']