Read the text to answer the question that follows. Unless you're shot in the head or hit by a bus, your immune system has a major and direct influence on your life span!Under normal circumstances the immune system acts for the good of the host - preventing infection and cancer.However, it can sometimes seem to be acting in a negative manner by actually causing disease rather than preventing it. Disorders in an individual'immune system can result in conditions of varying severity from affecting quality of life through to death. Often described as the "Goldflocks phenomenon", the activity of the immune system can result in disorders through either not reacting readily enough or by eliciting an immune response too promptly. In the first instance, where the immune system is not responsive enough, immunodeficiency diseases can occur, often resulting in recurring and life-threatening infections Immunodeficiency can arise from a number of sources the result of a genetic disease, such as in the case of severe combined immunodeficiency (SClD) from the use of pharmaceuticals, such as immunos uppressive drugs; or through an infection, such as acquired immune deficiency syndrome (AIDS) that is caused by the retrovirus HIV. In situations when the immune system is hyperactive and works more effectively than it should, the result can be an attack on normal tissues, as if they were foreign organisms. This can result in autoimmune diseases such as diabetes mellitus (type I diabetes), rheumatoid arthritis lupus enythematosus, coeliac disease and allergies to name but a few. Immunodeficiency can occur when one or more components of the immune system are defective or inactive The ability of the immune system to respond to pathogens is reduced in both the very young and the elderly.with immune responses starting to decline after the age of 50 on average due to immunosenescence . In developed countries, obesity.alcohol consumption and drug abuse are common causes of poor immune function. However, maloutition is the most common cause of immunodeficiency globally due to the often poor diet of individuals in developing countries. According to the passage which of the following is TRUE about immunodeficiency? A. It can occur when the immune system is responsive B. It is not very serious and dangerous for health. C. It attacks normal tissues and foreign organisms. D. It never takes place in developing country. E. It is mostly caused by lack of nutrition.