Final answer:
The National Ensign is flown at half-staff to honor a military victory or to signify mourning and respect during periods of national tragedy or on designated days of remembrance.
Step-by-step explanation:
The National Ensign, more commonly known as the national flag, is flown at half-staff on some occasions to signify a period of mourning or paying respect, often after the death of a significant figure or figures, during national tragedies, or on certain days of remembrance. This practice is a sign of respect and national sorrow. The answer to the student's question is that the National Ensign is flown at half-staff to honor a military victory.