defend 指用武力或其它措施保护某人/物在面临危险时不受损害；

protect指利用各种安全防御措施，尽力照顾某人/物，以使其不受损害；

guard意为“留心守望，警戒”，防止可能的攻击或侵害。如：

 ① It is the duty of every Chinese citizen to defend his motherland.

 ② Two big dogs guard the farm.

 ③ Clothes protect us from cold.

请完成下面的一些练习。

① We shall ___ our island, whatever the cost may be.

② Here we are well ____against a surprise attack.

③ Soldiers ___ the research center with guns every day.

④ Put on a thick coat to ____ yourself from the cold.

⑤The policemen were on duty around the clock to ____the city against attack.

答案：

①defend ② protected ③guard ④protect ⑤guard