a reasonable excuse的用法和样例：
- A cat caught a cock, and took counsel with himself how he might find a reasonable excuse for eating him.
- Failure to provide a breath ecimen without a reasonable excuse can result in three years' imprisonment and a driving ban of two years， the same for drink-driving.
- You are fortunate to have such a reasonable father.
- He gave me a reasonable explanation.
- He was feeling after a reason for their curious behavior.