Complete the sentences with for or since. 1 i've been playing the piano five years. 2 he's been working on that project months now, and he still hasn't finished! 3 you've been working on the computer …………..six this morning. have a break ! 4 we've been going to latin american dance classes ………..2004, and we're quite good at the tango now. s i've been reading this book ……… three weeks now. 6 we've been waiting here …… hours !