解释以下缩写词的含义：WHO，NASA，UNESCO，SIM card
WHO: 世界卫生组织 (World Health Organization)
NASA: 美国国家航空航天局 (National Aeronautics and Space Administration)
UNESCO: 联合国教科文组织 (United Nations Educational, Scientific and Cultural Organization)
SIM card: 电话卡 (Subscriber Identity Module card)