False. There are actually 9 essential amino acids that are needed to make a complete protein that is necessary for the dietary needs of a person. These amino acids includes Tryptophan, Isoleucine, Threonine, Lysine, Leucine, Valine, Methionine+Cystine, Phenylalanine+Tyrosine and Histidine. Generally, a complete protein can be gained from animal foods such as fish, poultry, animal meats and eggs, but it can also gain from selected plant foods as well. Incomplete protein can also become a complete protein when 2 or more incomplete protein are combined.
Vitamin C is water-soluble, ascorbic acid supplement to our body. We get vitamin C from citrus fruits, tomatoes and of course vitamin C tablets. Too much vitamin C or overdosage will cause indigestion, diarrhea, cramps, hair loss, nausea and nerve damage to the person. Daily recommended dosage is until 90 mg per day.
A cause for infection is pathogens entering the body. This is either to a disease that's being transferred from one being to another, or through toxins, wounds, and similar things. Most commonly, when fighting the infection, the body produces white blood cells to combat the infection, which in combination with medication usually defeats the infection.
A good idea what one could do in the off-season (considering one would do seasonal sports such as skiing) would be to either engange in activities that will preserve fitness - b, or to relax and recuperate; depending on the desire and wishes of the person - a.