微课内容说明：Step1.要求学生找出教材中含有现在完成时的句子Gooverthenewsstory,Boymissing,policepuzzled,andfindthesentencesusingthepresentperfecttense.学生将找到下面的句子.1.PoliceinAmericahavesteppeduptheirsearchforafifteen-year-oldboywhowentmissing…2.Thisincidenthasreceivedgreatinterestduetoreportsof…3.Ihaven’tseenJustinsince.4.It’shappenedtome!5.Whenasked…,whohastakenchargeofthecase,told…6.So,whilewehavenotdismissedtheidea,wearelookingintootherpossibilitiesaswell.Step2现在完成时的定义提供更多例句Step3带领学生回归教材，这是全课的重点和难点。
