I don't know: I think

I think "which" is a complement here, so the sentence should be " I don ' t know which the best is." But if it's a subject in the first sentence, how come it's not in the second? I didn' t know she's a vegetarian- I didn' t know until just now, when someone told me." I didn' t know she's a vegetarian during that event- The reason why didn' t is used here is to refer back the specific time-frame in the past. Does my instinct on the use of didn' t makes sense?Correct me if I 'm wrong.! 歌词是“Even though sometimes，you don’t know who I am”，歌名是《I Am You》。 歌名：I Am You 歌手：Kim Taylor 歌词： La di da di da da La di da di da da La di da di da da La da da I am tied by truth like an anchor 我被像锚一样沉重的真相困住 Anchored to a bottomless sea 牢牢地扎在在无边无际的海洋 I am floating freely in the heavens 我自由自在地游走在天上 Held in by your heart's gravity 被你深深吸引着 All because of love 这 ... i don t know和I didn't know的区别两者意思一样，只是时态不一样，don't是现在时，didn't是过去时。