a struggle for existence的用法和样例：
- The struggle for existence, in the case of the newspaper, has been a struggle for circulation.
- A struggle for existence inevitably follows from the high rate at which all organic beings tend to increase.
- A struggle for power took place within the company.
- It was a struggle for her to make him understand.
- A struggle for survival ensues (inference).
- Those variants will be preserved in the "struggle for existence".