请和你的同学一起讨论讨论，找出答案。

    Tom, Sam, Jim and Jack live in a building of four floors. They live on different floors. They have different jobs―an engineer, a worker, a teacher and a doctor. Tom lives above Sam, but below(在下面) Jim. Jack lives on the third floor. The doctor lives above the teacher, but below the worker. The engineer lives on the ground floor. What are their jobs? Which floor does each of them live on?

在中央电视台《星光大道》节目中，经常看到有些年轻选手落选后，坦然面对观众说：“不要紧，我还年轻，还有机会再来。”下列对此分析正确的是（     ）

世界上第一个把人类送入太空的国家是（  ）

如图，已知线段AB，分别以A、B为圆心，大于$\frac{1}{2}$AB长为半径画弧，两弧相交于点C、Q，连接CQ与AB相交于点D，连接AC，BC，E为AC的中点，连接DE，当线段AB=4，∠ACB=60°时，△CED周长是____