The girl (always) washes dishes after supper.（對括號部分提問）
答案是：How often does the girl wash the dishes after supper?
how often 指每隔多久,主要用來對頻度副詞或狀語(如：once a week,three times a month 等)提問.usually/ sometimes/always/often等詞在英文中被稱為“頻度副詞”.
例如：
1、The students (always) wash the clothes.（對括號部分提問）
How often do the students wash the clothes?
2、I play football (once a week).（對括號部分提問）
How often do you play football
希望能夠幫到你.