题目

How do you study every day? You may answer it in one second: have classes at school, take notes and do homework. Feeling a little bored? There are other ways that can make learning interesting and varied(各式各样的). It's called digital learning. Digital learning is a way to help students learn by using the Internet. There are three important kinds of digital learning. Apps are computer software applications(应用). People can download them on their mobiles. The other two kinds are social networking services, including Weibo and WeChat and websites. Each one of them is like your teacher.美国内战前夕，南方种植园经济实质上是 [    ] A.英国完全控制的殖民地经济　　  B.欧洲移民发展起来的奴隶制经济 C.种植园主经营的奴隶制经济　　  D.使用奴隶进行生产的资本主义经济