be seen to leave 和be seen leaving哪个对?为什么?

关于be seen doing 和 be seen to do once to be seen 和once being seen的区别 remain to be seen为什么等于appear/seem to be to see & to be seen be seen to do sth 和 be seen do sth 有什么不同?举实例说明 sb be seen to do sth 和 sb be seen do sth 有什么不同? 为什么是remain to be seen 而不是remain to see people can---------- running everywhere.see 和 be seen选哪个 He was nowhere to be seen.为什么要用不定式 be seen to do和doing有神魔区别 can be seen 和 can been seen 的区别? he was nowhere to be seen.