a bump on the head的用法和样例：
- A bump on the head caused her amnesia.
- She got a bump on the head when she fell off her bicycle, but thankfully she wasn't hurt.
- She tripped over a bump on the road.
- The staff were unaware that Fiona was an insulin dependent diabetic and was merely suffering from hypoglycaemia and a bump on the head.
- The bike hit a bump on the road.