不啰嗦，直接上菜：
1. on the hill在山上
A truck ran out of control on the hill.
一辆卡车在山上失去了控制。
You will see the chapel on the hill to your left
你会看见那座小教堂在你左侧的山上。
Recent excavations testify to the presence of cultivated inhabitants on the hill during the Arthurian period.
最近几次发掘证实了亚瑟王时期这座山上有农耕人口居住过。
2. in the hills在山区，在丘陵地区，山里
一般不说in the hill。如：
I love walking in the hills.
我喜欢在山中散步。
Here in the hills, the light failed more quickly
在山区这儿，天黑得更快。
He often took long walks in the hills.
他经常在山中久久漫步。
A smallholding in the hills could not support a large family.
山间（区）的一小块耕地是不可能养活一大家人的。
Nearby, nestling in the hills, was the children's home
孩子们的家就在附近的山里。
Ellen spent the day in the hills and sought me out when she returned.
埃伦在山里待了一整天，并于回来后找到了我。