has worked;他从晚上7点,就开始做数学题.
has worked他做数学题做了2小时了
will
我肯定他会在1小时之内完成这道题.
祝好!___the Blacks___(visit) the Great wall before？Yes,they____.___the Blacks___(visit) the Great wall before？ Yes,they____.Havevisitedhave .希望我的回答对您有帮助，祝好！谢谢 这个是现在完成时阿呵呵，没错的啦。 不信你明天问老师哈。