Methods used to reduce sulfur dioxide emissions from smokestacks are an attempt by humans to a lessen the amount of insecticides in the environment b eliminate diversity in wildlife c lessen the environmental impact of acid rain d use non chemical controls on pests

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.