为什么-（ ）is on duty today?-I am.A,who B,whose C,which 选什么 为什么

Who is on duty today?为什么用on duty is on duty today who is on duty The police are duty on the duty on road.这里为什么用are 而不是用is? 2.Do you know ______ else is going to be on duty today?（who,whom） it is your turn to be on duty ,为什么用so it is,而不用so i am He felt it his duty to.为什么不是He felt it is his duty to . who is on duty today what is on duty today? _____lily______?A.Is,on duty B.Dose,on duty whose turn is it-------（be） on duty today 为什么-（ ）is on duty today?-I am.A,who B,whose C,which 选什么 为什么 It is a b---- responsibilily（责任） to be on traffic duty.填词It is a b---- responsibility（责任） to be on traffic duty,but I like it. It's on duty to keep our classroom clean 改为同义句_______ ________ our classroom clean is our duty. your duty is to obey . I think he is on duty today.为什么用ON,可以去掉吗 It is our duty to ＿（study） hard. it is your turn to be on duty.（ ）A so am I Bso it is CSo Iam Dso is it 闹不清