外交是综合国力的延伸，国家的强弱直接影响外交的成败。下列几幅图片反映了新中国外交的曲折历程。

顾炎武指出：“保国者，其君其臣，肉食者谋之：保天下者，匹夫之贱与有责焉。”与该观点相呼应的先秦儒家思想是（   ）

目前已知的动物约有150万种，根据动物的体内有无脊柱，可以把动物分为两类：一类是____，另一类是____．

根据句意，写出括号内所给单词的适当形式。
It's my cousin's ____ (twenty) birthday next week.
The weather in Nanjing is ____ (pleasant) in summer. It's always too hot.
People screamed with____   (excite) when the match began.
He was so tired that he fell____ (sleep) soon after he went to bed.