1.He ____(know) a lot about Europe.Let's go and ask him.2.I ____(be) to Paris twice,but I have never been to London.3.The teacher ____(walk) into the classroom with a book in his hand.Be quiet!说明道理,_百度作业帮 1.He ____(know) a lot about Europe.Let's go and ask him.2.I ____(be) to Paris twice,but I have never been to London.3.The teacher ____(walk) into the classroom with a book in his hand.Be quiet!说明道理, 1.He ____(know) a lot about Europe.Let's go and ask him.2.I ____(be) to Paris twice,but I have never been to London.3.The teacher ____(walk) into the classroom with a book in his hand.Be quiet!说明道理, he是第三人称单数,所以know后面加s.2.have been to 对照后面的内容就可以.have been to 表示去过,已经回来了.have gone to 表示已经去了,还没回来.3.is walking. be doing表示正在做.老师正走进. 1. knows 一般现在时，陈述事实：他对欧洲很了解。2. have been 我曾经去过巴黎2次，现在完成时3. is walking 根据后面Be quiet判断，老师正走进教室，大家安静！ 1.knows 2.have been 3.is walking knows (一般情况）have been （已经到过2次，后面半句也有提示）is walking （正在来，后面Be quiet! 翻译也有提示） knows 就是普通的一般时态have been 注意后一分句也是用这个，表示到现在已经去过两次，正在那个地方用have goneis walking现在进行时 knows 因为HE是第三人称单数形式，所以加Shave been 意思"我曾经去过（现在已经回来了）”如果是“已经去拉，但是还没有回来”就用have gone to is walking 由Be quiet可知，是现在进行时，所以用动词ing 形式 一般现在时表事实2 have been 完成时表示去过两次3 is walking 个人觉得应该用进行时，因为说话人让别人Be quiet的同时他看见老师走进来 1.He _KNOWS a lot about Europe.Let's go and ask him. 一般陈述句,用第三人称单数2.I HAVE BEEN to Paris twice,but I have never been to London. 表示去过某地,用have been to somewhere, 表示去了某地,用have gone to.