Two men are walking in the park. One is Mr. Brown, a worker, the other is Mr. Black. Mr. Brown is going to a chair. It is next to the road. Mr. Black is after him. Mr. Brown finds Mr. Black. Now Mr. Black begins to walk faster (更快). Because he wants to get to the chair before Mr. Black. Now Mr. Black begins to walk faster because he also wants to get to the chair first. Then they both run. Mr. Black runs faster than (比) Mr. Brown. So he gets to the chair first and sits down on it. Mr. Brown runs after Mr. Black. When he gets to the chair. He sees Mr. Black sitting on it. He is sorry to show a notice(通知)with the words“Wet Paint(油漆未干)”to Mr. Black. Now Mr. Black knows why Mr. Brown is going to the chair.

由此可写出各步反应的化学方程式．硫及硫的化合物间的转化关系可表示为：

南方地区夏季高温，素有“三大火炉”之称的城市有（   ）

如图为人体循环系统的部分结构示意图，据图回答．