A large number of sheep died on a farm. An expert dissection revealed that there was a wild vegetable residue in the stomach of the dead sheep. After testing, the wild vegetable was infected with a germ that could release a substance that has devastating damage to the mammalian central nervous system. Small amounts can cause immediate death, but the farmer said that their whole family also ate this wild vegetable, but it was no different. Which of the following is true to best explain the situation? ['The bacterium is only harmful to mammals and does not harm the normal growth of wild vegetables.', 'The bacterium was found in some healthy people.', 'The germ only infects the roots of wild vegetables, the whole wild vegetable is swallowed by the roots, and people only eat the young leaves of wild vegetables.', 'The family only ate one wild vegetable.']