英语翻译为什么用have been 不懂

英语翻译为什么用have been 不懂 there have been great changes为什么用have been I have been sick since yesterday.中have been 是什么是时态为什么要用been. 英语：这里为什么要用have been 英语翻译为什么用There have been?我不常见到这样用啊? there have been many great inventions 为什么用have 英语翻译不懂为什么人会变做狗, I have been busy yesterday afternoon为什么要用have been busy而不用ha all my favorite bands have been British bands.为什么用have been 为什么 are more likely to have been,可以这样用?have been 可以去掉吗? 他们结婚十年了 They have been married for ten years 为什么要用have been 英语翻译Women have been discriminated against,and they have been