With your brother’ s help, I’ve made great progress in English and I really want to do something for him _____.

A．in turn

B．by turns

C．in return

D．in answer

有a、b、c、d、e五位同学一起比赛象棋，每两人之间只比赛1盘，统计比赛的盘数知：a赛了4盘，b赛了3盘，c赛了2盘，d赛了1盘，则同学e赛的盘数是______。

A．1盘

B．2盘

C．3盘

D．4盘