【正确答案】 A

【答案解析】[解析] while=whereas“而”，并列连词，用于对比，表示“当……时而……；当……时却……”；while前后的两个分句是并列关系。可引导对比关系的最常用的连词是whereas，此外还有where，这三个连词都是谈论两个正在发生的或处于静止状态的相反的事物，如：Some praise him, whereas others condemn him. They want a house, where we would rather live in a flat. C项when也可引导对比关系，不过它不同于上面那三个连词，它用于表示某一事物现在所处的状态或“(正在……)而它本该……”，如：He walks when he might take a taxi. Why are you here when you should be in school?D项at the same time“尽管如此”，如：He did pass the test, but at the same time he didn't know the subject very well. meanwhile“与此同时；在……这段时间”，是副词。