“Your sister is when to start playing the piano ”?请不要用翻译软件在这里乱说。狗屁不通!
正确的应该是:
when did your sister begin to play the piano?或者when did your sister start to play the piano?
when是什么时候的意思,your sister 是你妹妹的意思,begin或start 是开始的意思,play the piano是弹钢琴的意思。在英语里面疑问副词:when要放在这句话最前面。