In some countries,students have to wear ------ uniform to sc

In some countries,students have to wear ______ uniform to school.A) a B) an C) the D) /The Smiths_______in this housing estate,didn't they?A) used to living B) used to live C) are used to live D) are used to livingYou should apologize to Mr.Li__________you know you did something wrong.A) whenerver B) since C) until D)unless