阅读下面短文，将短文中画线部分的句子翻译成中文
                                                                                How Much Water Is Needed a Day?
   Many people think they should drink eight glasses of water a day．Why? Because that is what they have been told all their life．But a new report on science gives some different suggestions：people should drink according to their bodies．____ They should drink as much water as they would like to drink．
   The report says most people meet their daily needs for water by letting thirst be their guide．It also gives people some good suggestions：women should get about 2.7 liters（升）of water every day，while men should get about 3.7 liters．
   There is an important difference．____ The report doesn’t tell people how many glasses of water to drink．Instead，the experts say it may not be possible to know how many glasses people really need．This is because the daily want of water can include the water in foods．

观察如图人的心脏内部结构示意图，图中①和④所指的腔分别是心脏的（    ）