I could run fast when I was young, but I can't run fast now.我小时候跑得很快，但现在不行了。When I was younger I could run fast, but I can't run fast now.我年轻时能跑得很快，但现在不行了。It's something I can't tell you – not just now, anyway.这事我不能告诉你，至少现在不行。Not now Stephen, I'm busy.现在不行，斯蒂芬，我正忙着呢。