单选题 Although there arc many predictions about the future, no one knows for sure ______the world would be like in 50 years.
【正确答案】 D
【答案解析】[解析] 谓语动词knows后面的宾语从句中缺少一个引导词，根据句意和，结构，该引导词应在从句中作 like的宾语，表示什么样，故只能用what。