321　guard，safeguard和defend

① guard指“用极度的小心和戒备实际的或潜在的危险”。

These special branch men were appointed to guard the Prime Minister. 委派这些特种警卫人员来保护总理。

② safeguard是指“保全使之完好无损”，“对长远的可能发生的事情深谋远虑”。

Saving money regularly will help to safeguard one's old age from want. 不断按时储蓄将会使晚年免于匮乏。

③ defend强调目前所面临的危险，指“用武力或其他对策进行保护、辩护”。

It is the duty of every citizen to defend his country when it is attacked by the enemy. 国家受到敌人攻击时，保卫国家是每一个公民的职责。

He is so obstinate that he still tries to defend his theory，although it has been proved wrong. 他那人固执极了，尽管他的理论已经证明是错误的，他还是设法替自己辩护。