题目

设⊙O的半径为2，圆心O到直线的距离OP=m，且m使得关于x的方程有实数根，则直线与⊙O的位置关系为(    )      A．相离或相切B．相切或相交C．相离或相交D．无法确定 答案：B解析:略If you want to watch and know something about birds, you must find a good place near the bird nest（巢）.Birds sit on eggs and take care of their babies from April to June. Because the baby birds are too young to leave the nest, parents often go to look for food and come back in several minutes. So it is good to watch birds. When we watch birds, we’d better hide ourselves in a close place to the nest, and it’s better to use binoculars(双筒望远镜).But how to make a bird nest? A good bird nest must be very fine, strong, thick and comfortable. If you want to make one, please follow these:a) Each nest must have six boards（木板）. Don’t make the boards too slippery（滑）.b) Dig a small hole in the front of the nest as a “door”. The “door” is big enough so that birds can fly in or out easily.c) Make sure the rainwater can’t go into the nest.d) One piece of the board should be easy to open.e) Don’t forget to colour the nest.1. The most important thing in watching birds is to .A. look for a place near the bird nestB. climb up to the treesC. catch a birdD. kill a bird2. We have to hide ourselves to , when we’re watching birds.A. take better care of themB. use the binocularsC. make them do everything as usualD. kill them at last.3. If we make the nest too slippery, .A. it won’t be very beautiful B. it won’t be easy to makeC. it won’t be strong D. it’s very difficult for birds to hold or stand on it4. We should leave a hole in the front of the nest so that easily.A. we can clean the nestB. birds can fly in or outC. we can hang（挂）D. we can make it5. What’s the best title of this passage?A. Birds are man’s friends B. How to catch birdsC. Watching birds and making bird nests D. How to keep birds