过去常常：Used to always do sthing in the past.
我过去常常很晚睡觉.
I used to always sleep late in the past.
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被用作: Sthing were/was used as sthing.
照片被用作广告
The pictures were used as advertisement.
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习惯于：I am used to doing sthing.
我习惯很快的完成作业.
I'm used to doing homework quickly.
不知道这是不是你想要的?