a last line of defense的用法和样例：
- Their purpose is to serve as a last line of defense against the Horde.
- "We are looking for a last line of defense and that defense has to be lethal to counter lethal intent," said Gregg Overman,spokesman for the Allied Pilots Union representing 13,500 American Airlines pilots.
- The safeties are the last line of defense (farthest from the line of scrimmage) and usually help the corners with deep-pass coverage.
- We had both given up on our dad but felt compelled to do something. He was our father and we were his last line of defense.