Rick and Mary are from America．Now they are working in Tianjin．They can speak a little Chinese．Every morning they get up very early．Then they go to work by car.·They are very busy．They have lunch at the factory．①After lunch they work again．They finish their work very late．  In the evening they take Chinese lessons(上汉语课)．They want to talk with Chinese people．They often say，“Chinese people are very friendly(友好的)．”②They like to stay in China and they like to work with Chinese people．

根据短文内容，完成下列题目。

数学模型是用来描述一个系统或它的性质的数学形式。调查发现某种一年生植物（当年播种、当年开花结果）的种群中存在下列情形：①因某种原因导致该植物中大约只有80%的种子能够发育成成熟植株；②该植物平均每株可产生400粒种子；③该植物为自花传粉植物。目前种子数量为a，则m年后该植物的种子数量N可以表示为

①小华告诉小丽，他还____（hái  huán）要去图书馆还____（hái  huán）书。

②放学了，同学们____（在  再）校门口和老师说____（在  再）见。

③中____（午  牛）的太阳太大了，老____（午  牛）热得直喘（chuǎn）气。

④用音序查字法查“准备”的“准”，应先查字母____（Ｚ  ZH），再查音节____（zun  zhun）。

We mustn't            matches.