a tenable fortress的用法和样例：
- This is a tenable approach and will do us much good.
- Semantic paradox is not a tenable proposition, no m atter its hypothesis is true or not, from this point of view, it can be called " neutral proposition".
- The easiest way to capture a fortress is from within.
- The lectureship is tenable for a period of three years.
- There is a vein of melancholy in his character.