fall over a bike还是fall off a bike啊?

fall off a bike
从单车上摔下
fall off 从.掉下
fall over a bike
被单车绊倒
fall over
意外地从…上跌落,掉下来
The car fell over a cliff and the driver was drowned.
汽车从悬崖上翻下来,司机溺水而亡.
The cascade falls over a tall cliff.
瀑布从高高的悬崖上倾泻下来.
被…绊倒
He fell over a rock in his path.
他在小路上被一块石头绊倒了.