几个现在完成式的英语问题.1.already和yet的区别.2.You are late.The film began 10 minutes ago.(同义句)A:You are late.The film _____ _____ _____ for 10 minutes.B:You are late.It ____ten minutes since the film _____.要求说明每个题的知识点.

1， Yet and already are both used when talking about the possible completion of an action by or before a particular time. They are mostly used with the perfect tenses (in US usage also with the simple past). *yet和already均用以表示到某时或某时前可能完成的动作. 两者多与完成时态连用（在美式英语中还与简单过去时态连用）. Yet is only used in negative statements and in questions *yet只用於否定的陈述句及疑问句: `It's time to go. ' `I'm not ready yet.' ‘该走了.’‘我还没准备好呢.’ * Are you out of bed yet? 你已经起床了吗? Already emphasizes the completion of an action. It is usually used in positive statements*already强调动作的完成, 常与肯定的陈述句连用: By midday they had already travelled 200 miles. 到中午为止, 他们已经走了200英里了. Already can be used in questions to express surprise *already可用於疑问句, 表示惊奇: Have you finished lunch already? It's only 12 o'clock! 你已经吃过午饭了吗? 现在才12点钟啊!
2，A.has been on 现在完成时表示过去进行了一段时间且还有可能继续下去，这里for ten minutes是一段时间电影肯定还会继续的，所以A要用has been on
B. is, started. 本来用since引导从句时，主句是要用完成时的，但一种特殊情况除外，就是这里主句是表示一段时间，则主句可用现在完成时，也可以用一般现在时，就是说这里可以填has been，也可以填is，但既然只有一空，当然填is了；至于第二空，应该没什么疑问吧，“电影开始”是过去发生的一件事，用一般过去时

1.alreay 用语肯定句 yet 用于否定句
2.A.the film has already began for 10 minutes.
begin 瞬间动词 has already began for 10 minutes 现在完成时表示该事件10分钟前已经发生
B.It has been ten minutes since the film began.
这里用 it has been 表示从开演到现在已经持续了10分钟了 has been doing 表示事件已经发生而且延续到现在