A Policeman and a Thief  
One day a policeman was taking a thief to the city . On the way , they saw a shop . The thief said . “ Let me go into the shop to buy some bread . We can eat it in the train . ”
The policeman agreed . The thief went into the shop and ran out of the back door . When the policeman knew that , he began to look for the thief everywhere . At last the policeman caught(抓获) thief again . They went on to the city . On the way they came to the same shop . The thief wanted to buy some bread again . “Oh , no . ” said the policeman , “You did that before , and you ran away . This time I^’ll go into the shop and buy bread . You must wait here for me . ”

水具有反常膨胀的特性．如图所示为水的密度在0℃～10℃范围内随温度变化的曲线．根据图象可知，温度等于____ ℃时，水的密度最大；在0℃～4℃范围内，水具有____ （填“热胀冷缩”或“热缩冷胀”）的性质．