what do you do(on) your birthday为什么要用on

what do you do on what do you do on the weekend what do you do on the weekend? What do you do on Sundays? what do you do on sundays? What do you do on weekends是什么意思 What do you usually do on weekends? What do you do on the weekend? What do you often do on what do you do on sundays?汉语 What do you do on Sunday是什么意思 What do you do on Sunday morning? what do you do on thanksgiving What do you usually do on Saturdays? What do you do on Saturdays What do you do on week-ends? what do you do on saturdays?是什么意思 do,what ,do ,you ,Thanksgiving Day ,on )