单选题 The United States of America (USA or U.S.A.), commonly referred to as the United States (US or U.S.), America, and sometimes the States, is a federal republicconsisting of ______ states and a federal district.
【正确答案】 C
【答案解析】[解析] 本题考查美国国家概况，美国是由“50个州和1个联邦特区”组成的国家，因此，答案是C。