综合短文填空，选择正确单词填入相应的空格.

    People never travel as often as today in China. In the past, few people could travel on ____ to other countries. But today more and more Chinese people travel ____they now are becoming richer and have enough money for travel. The special plane for tourists ____ travel____ expensive than ever before. Most people enjoy ____ countries that are different from ____own. They also like to meet people and eat new food. Tourism causes many____  in Chinese people’s lives. People build new hotels and ____some people____ interesting places to ____ . Now Tourism is a big business.

某校学生户外社团计划到如图（某区域等高线图）所示区域开展户外活动．读图完成下列要求．

下列给出5个命题：

①对角线互相垂直且相等的四边形是正方形

②六边形的内角和等于720°

③相等的圆心角所对的弧相等

④顺次连接菱形各边中点所得的四边形是矩形

⑤三角形的内心到三角形三个顶点的距离相等．

其中正确命题的个数是（　　）