Fact 1: Immunodeficiency occurs when the immune system is not working properly. Fact 2: Iron deficiency causes anemia and it weakens the immune system. Given the two facts above, answer the question "What can low iron cause?" with the following options: - contamination - Pollution - decrease stamina - harmful substances - immunodeficiency - the ground shaking - cloudy and rainy weather - Temperature changing
A:
immunodeficiency