单项选择题 By the mid-1920s, American film industry came into the hands of a few powerful companies, which controlled production, distribution and exhibition. Normally, they were called “the Big Five” and “the Little Three” as well.________

判断题 天线的驻波比反应终端负载与特性阻抗匹配程度。正确错误

单项选择题 4. 下列哪种电子货币不是目前网上常用的？ A. Q币 B. 银行卡型电子货币 C. 电子支票 D. 电子现金