精选优质文档-倾情为你奉上 必修四 Unit 31. up to now 至今为止 常用于现在完成时 He has lived in HZ up to now. over the past/ the last two months 在过去的两个月里 句子用现在完成时I have written 2 books over the last 3 years.2. at a time 每一次 Please ask one question at a time. at one time 曾经 At one time, he was a bad boy.at the time 在当时 Life was hard at the time. at all times 一直 Please pay attention to them at all times.3. common 常见的 The flower is common in HZ ordinary 一般的 His