新概念英语2册56课问题1.once a year,a race is held for old cars.请问能否把a去掉改成：once a year,race is held for old cars.为什么?2.old car race is held ones a year.请问能否加个an改成：an old car race is held ones a year

新概念英语2册56课问题1.once a year,a race is held for old cars.请问能否把a去掉改成：once a year,race is held for old cars.为什么?2.old car race is held ones a year.请问能否加个an改成：an old car race is held ones a year 新概念英语2册56课once a year,a race is held for old cars. old car race is held ones a year. 请帮我分析下句子结构,关键是once a year 新概念3册24课最后一句的 once upon a time怎么理解, 英语新概念1册99课问题The doctor says that he will come at once.医生说他马上就来.问1；句中的 will 是什么词性?是助动词吗?问2；will come是固定搭配吗?will come at once是固定搭配吗?willn.意志；决心；情 青少版新概念英语2a练习册11课答案 新概念英语第三册第5课的一个语法问题The editor at once sent the journalist a fax instructing him to find out the exact number of steps and height of the wall..instruting 为什么要用ing形式呢? 英语 （出自新概念英语第三册课后练习第三课）The city had once known ___.a.a prosperity b.the prosperous c.the prosperity d.prosperity答案是d,为什么前面不可以加冠词呢? 青少版新概念英语2a 新概念英语问题, straight away 和after a while 有什么区别?新概念英语第二册49课的最后一个问题. 新概念英语2练习册56课答案亲们, 新概念英语2 第9课的一个问题 求助：What does a cold welcome refer to? 新概念英语第二册16课课文提个问题,中文是课文中的语法问题。 新概念英语青少版2A练习册第四单元答案 .谁知道新概念英语青少版2A练习册Unit15答案? 新概念英语青少版2a练习册unit15答案 新概念英语青少版2A 第13课 卡兰津人课文 新概念英语2作业本69课答案A部分,急