A man got the lawn mower out of the garage and worked on (the ground of ) the yard. 有个人把除草机从车库里推出来,然后就在院子里（的地上）忙活起来。

They found the farm green with vegetables, the little house livable and homey. There was a tractor and a good car in the yard. 他们看到农场上长着绿油油的蔬菜，小屋布置得舒适温馨，院子里有辆拖拉机，还有一辆不错的汽车。

【参考解析】

on the yard = on the ground of the yard 在院子里的地面上，单纯的指范围，没有相对性。

in the yard 在院子里，有相对性，表明不是在院外，而是在院内。