题目内容
设R1,R2是集合A={a,b,c,d}上的两个关系,其中R1={(a,b),(b,c),(d,d)},R2={(a,b),(b,a),(b,c),(c,b),(d,d)},则R2是R1的_____闭包。
查看答案
搜索结果不匹配？点我反馈
更多问题
以下语句中_____不是命题.
已知无向树T,则T不具有的性质是。
If you __________ (1) find out what it is like __________ (2) the tropical jungle, you should make a trip on the river. This is better than walking through the trails in the forest, as these are often blocked by undergrowth that gets __________ (3) in your feet and makes traveling difficult. In a dugout canoe, you can sit back and enjoy the scenery while the guide __________ (4) it along the rivers that __________ (5) their way through the forest. Everywhere you go, you can hear the clatter of birds, hidden __________ (6), deep in the jungle. At other times, they are clearly visible, circling __________ (7) overhead. And you can also see some of them __________ (8) about in the clearings and others __________ (9) on the __________ (10) waters. But birds are not the only wildlife. From time to time, you can spot enormous black fish __________ (11) about in shallow water. Or if you look closely enough, you can see some small animals __________ (12) in and out of the bushes. Indeed, the whole jungle __________ (13) with a huge variety of animal life, guaranteed to make your trip a __________ (14) event that you will never forget.
The Amazon is a world of trees and water in the middle of South America. It's the world's mightiest river, __________ (1) through the world's largest tropical rainforest.Most trips to the Amazon are based in either a boat or a lodge. If you __________ (2) travelling by boat, many organised trips __________ (3) travelling on the main river with side trips on smaller tributaries, either in motorboats or in canoes. If you prefer __________(4) the rainforest on foot, you can usually find some local people who are ready to __________ (5) you through certain parts of it despite all kinds of difficulties. If you want a little more __________ (6), the upper Amazon flows off the Andes, creating ideal opportunities for rafting through __________ (7) visited areas.While the overwhelming beauty of the Amazon lies in its __________(8) and complex nature, it is also a place where plants are king, insects come a close second, and animals hide to __________ (9). With a good guide you will see many birds and some mammals, including monkeys, but only if you are very __________ (10) will you see a jaguar (美洲虎).
微信支付 
支付宝支付