Which one of the following, if true, would most seriously weaken the proponents' argument regarding the safety of using altered Pseudomonas syringae bacteria to control frost damage? A. Pseudomonas syringae bacteria are primitive and have a simple genetic constitution. B. The altered bacteria are derived from a strain that is parasitic to plants and can cause damage to crops. C. Current genetic-engineering techniques permit the large-scale commercial production of such bacteria. D. Often genes whose presence is responsible for one harmful characteristic must be present in order to prevent other harmful characteristics. E. The frost-damage experiments with Pseudomonas syringae bacteria indicate that the altered variety would only replace the normal strain if released in sufficient numbers.