如图，∠AOB是平角，∠AOC=30°，∠BOD=60°，OM、ON分别是∠AOC、∠BOD的平分线，∠MON等于（　　）

下列说法正确的是（　　）

①代数式$\frac{a}{b+1}$的意义是a除以b的商与1的和；

②要使y=$\frac{\sqrt{3-x}}{x}$有意义，则x应该满足0＜x≤3；

③当2x﹣1=0时，整式2xy﹣8x²y+8x³y的值是0；

④地球上的陆地面积约为149000000平方千米，用科学记数法表示为1.49×10⁸平方千米．

新疆地区昼夜温差大，瓜果特别甜，是因为（　　）

    It is necessary to relax ourselves after the exam. There are some kinds of  activities for us to take part in. First of all, we can go for a w____ along the bank of the river. We can also go to the movies or listen to music. What's more, joining in a sports club is a good c____, which can keep us healthy. For example, p____ football in the afternoon may relax ourselves. Above all, we should arrange(管理) our time p____ and live a regular(规律的) life. I hope all of us can have a wonderful time.