根尖的成熟区是植物吸收水分的主要部位，其主要原因是（　　）

某人在医院做了一次心电图，结果如图所示．如果心电图仪卷动纸带的速度为1.5m/min，图中方格纸每小格长1mm，则此人的心率为（   ）

已知f（x）=2^x+1，则f（2）=（　　）

语法填空

    July is coming. People all around the world are talking about their ____ (vacation). Parents would like ____ (help) their children relax. ____ (luck), they have two months off. Some people enjoy quiet life, so many of ____ (they) stay at home watching TV, using computers and so on. ____ some spend time differently. My pen pal Tony ____ blonde hair is a boy from the US. He says that ____ (America) like going to the countryside. Just like his big family, they often go to a farm. There, some can feed animals, some can play and ____ (other) can watch ____ nice sky and rivers. They can also taste delicious food. They are quite ____  (interest) in the life there.