1.【原句再现】…,which is said to be the longest border in the world not defended by an army or the police. (P 2)
【知识要点】defend/ guard/ protect
【诊断练习】用defend, guard, protect的适当形式填空。
①My brother is one of those who ____ our country at the boundary.
② Measures should be taken to ____ the environment.
③There are two soldiers ____ at the gate.
