how long is it since Beijing International Film Festival opened?这句话前面为什么用is而不是has been?不是说since前用完成时吗?为什么这道题不是呢回答的时候,最好第一说这句话的翻译,然后再解释原因,

How long is it since your father_____an engineer?（become） how long is it since you went to the seaside? how long is it since you last saw her?since 不是用在现在完成时吗 How long is it? how long ()you joined the league?A have B did C is it since D were how long do you think it is _____he arrived here?a.before b.since 1.How long is it since your sister _________(become)a teacher? The use about the word since.How long is it since you lived in shanghai?,is it as same as this sentence How long is it since you left shanghai? .Thanks for your help. Which is correct.Please explain it.1)How long has it been since this company was established?2)How long has the company been established? How long has it been since.这是什麼用法 意思 How long do u suppose it is ____ he arrived and began to work here A beforeB whenC afterD since -How long do you suppose it is ______ he arrived here?a,after b,since我觉得两个都可以. how long is it ___the class ___?A when .. begins B when .. began C since.. had begun D since .. began选择D 是为什么么呢 英语单选（关于since和before)How long do you suppose it is ＿＿ he arrived there?A.before B.since 两者有什么区别? How long is it ____ the metting___?A.When,began B.since,began C.when,begins D.since,has been begin 不是瞬间动词嘛 不是不能和how long连用的嘛?为什么不选D How long is it?同义句 How long is it 中文怎么读 HOW long is it's taii