a serious warning的用法和样例：
- The extinction of so many animals and plants has sounded a serious warning to mankind.
- We hereby give a serious warning to the gentlemen of the reactionary Nanking government. You must re-arrest Yasuji Okamura immediately and return him to prison without fail.
- Prime Minister Abdullah Ahmad Badawi must also issue a serious warning to the police force to stop abusing its powers to prevent custodial deaths in the future.
- He received a serious warning.
- The poor man has a serious disease of the liver.