Answer the question from the given passage. Your answer should be directly extracted from the passage, and it should be a single entity, name, or number, not a sentence.

Passage: Disorders of the immune system can result in autoimmune diseases, inflammatory diseases and cancer. Immunodeficiency occurs when the immune system is less active than normal, resulting in recurring and life-threatening infections. In humans, immunodeficiency can either be the result of a genetic disease such as severe combined immunodeficiency, acquired conditions such as HIV/AIDS, or the use of immunosuppressive medication. In contrast, autoimmunity results from a hyperactive immune system attacking normal tissues as if they were foreign organisms. Common autoimmune diseases include Hashimoto's thyroiditis, rheumatoid arthritis, diabetes mellitus type 1, and systemic lupus erythematosus. Immunology covers the study of all aspects of the immune system. Question: What acquired condition results in immunodeficiency in humans?
HIV/AIDS

Passage: Sometimes the prosecution proposes a plea bargain to civil disobedients, as in the case of the Camden 28, in which the defendants were offered an opportunity to plead guilty to one misdemeanor count and receive no jail time. In some mass arrest situations, the activists decide to use solidarity tactics to secure the same plea bargain for everyone. But some activists have opted to enter a blind plea, pleading guilty without any plea agreement in place. Mohandas Gandhi pleaded guilty and told the court, 'I am here to . . . submit cheerfully to the highest penalty that can be inflicted upon me for what in law is a deliberate crime and what appears to me to be the highest duty of a citizen.' Question: When many people are arrested, what is a common tactic negotiating?
solidarity

Passage: Southern California is home to Los Angeles International Airport, the second-busiest airport in the United States by passenger volume (see World's busiest airports by passenger traffic) and the third by international passenger volume (see Busiest airports in the United States by international passenger traffic); San Diego International Airport the busiest single runway airport in the world; Van Nuys Airport, the world's busiest general aviation airport; major commercial airports at Orange County, Bakersfield, Ontario, Burbank and Long Beach; and numerous smaller commercial and general aviation airports. Question: What is the second busiest airport in the United States?
Los Angeles International Airport