is on duty today

is on duty today who is on duty today what is on duty today? Who is on duty today?为什么用on duty Who is on duty today ?是什么意思 谢谢 whose turn is it ( ) on duty today on duty today who is ( ) duty today? whose turn is it-------（be） on duty today Today is my on duty for the day. ____is on duty today?Li Lei is.怎么填? on duty today 什么意思? whose on duty today改错 ( )on duty today?Wng Tao( ) Who is ___ duty today? is Han Meimei-----duty today? who is on duty I think he is on duty today.为什么用ON,可以去掉吗