阅读下面短文，在空白处填入一个适当的词，或填入括号中所给单词的正确形式。
Every country shares things ____ common: we value family and laughter, cherish food and health, and celebrate large ____(festival) and traditions. Yet within the similar things we share, there are unique parts of each country. One of characteristics that are famous of British people ____(be) their sense of humor, particularly self-mockery (自嘲). This is a type of humor that criticizes and undervalues oneself. For example, a fat person may joke: “I am on a new sea food diet. If I see food, I eat it.” This is ____ well-known self-mockery joke. It's difficult why self-mockery ____(tie) to the British people. But every nation's sense of humor comes from its culture and history. It could come from another British characteristic, modesty, ____(mean) not talking openly about your skills. This seems to be something that is similar to people in China, ____ modesty plays a big part in daily life. It also acts as a defense of our self-respect by playing down our skills, this can ____(less) the chance of people criticizing us. Another possible reason is ____ the British people do not take themselves too ____(serious).
和
两种同位素，