Which one of the following best summarizes the main idea of the passage? A. Recent field experiments with genetically altered Pseudomonas bacteria have shown that releasing genetically altered bacteria into the environment would not involve any significant danger. B. Encouraged by current research, advocates of agricultural use of genetically altered bacteria are optimistic that such use will eventually result in improved agriculture, though opponents remain wary. C. Current research indicates that adding genetically altered Pseudomonas syringae bacteria to the soil surrounding crop plant roots will have many beneficial effects, such as the prevention of frost damage in certain crops. D. Genetic alteration of a number of harmful phytopathogens has been advocated by many researchers who contend that these techniques will eventually replace such outdated methods as crop rotation. E. Genetic alteration of bacteria has been successful in highly artificial laboratory conditions, but opponents of such research have argued that these techniques are unlikely to produce organisms that are able to survive in natural environments.