中国这条东方巨龙“腾飞”的原因有    (       )

①以经济建设为中心,大力发展生产力  ②坚持***的领导 
③坚持改革开放                              ④广大人民的艰苦奋斗 

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。

    Mr. Green has ____bakery. Many customers come to buy ____(variety) of bread every day. ____ (say)that Mr. Green's bread is nicer and cheaper than ____in other bakeries. Children always ask their parents to buy Mr. Green's cake ____their birthdays because it tastes so delicious and looks so cute.

    Betty is Mr. Green's only daughter  ____usually helps in the bakery. However, she thinks her father very cold and complains to her mother: “Mom, why does Dad never say how much he loves me? Is it because he doesn't like me?” “Oh, my good girl,” says Mrs, Green. “You never know how proud your father is of you.     Nothing else in the world ____(mean) more than you to your father. When he's making cookies and bread, he is thinking of you. That's ____our cakes and bread are the ____(good). Sometimes when you've done something wrong and made him angry or sad, the bread that day must taste hard and dry. Your father may not say how much he loves you, ____ his bread does.”

酷爱科学的小李为了探究液化过程放热还是吸热，设计并完成了下面实验：

①将一定质量温度为t₁的冷水装入一个双层玻璃真空保温杯中，液面如图甲所示位置，标记为A。②向杯中插入导管，将100℃的水蒸气通入冷水中，发现杯中水面明显上升(假设水蒸气全部被吸收)。③一段时间后，停止通入水蒸气，移出导管后，杯中液面位置如图乙所示，标记为B，再测出此时杯中水温为t₂，比较发现t₂高于t₁。于是小李得出了液化放热的结论。