Answer: Symptoms of potassium deficiency appear on the lower portion of the plant first with chlorosis (yellowing) at the leaf margins followed by necrosis (death). Potassium deficiency can be caused by soil pH, extreme liming or calcium rich areas of fields, lack of soil oxygen or true soil deficiency.
Answer:
Because you body is introduced to the virus, it is familiar to it and can build up an immunity to the weakened form so when the actual virus invades, your body know what to do.
Explanation: