题目

It is important to teach your dog to guard you and the other members of your family to fight against danger Here are some tips on how to train your dog to protect you.【1】It is very important to introduce your dog to other people and let it interact with them. A good guard dog is friendly to the people around it. This exercise is very important because it will help the dog distinguish between good people and bad people. 【2】Use proper commandsA dog acts according to how it has been trained. The only way to do this is through com- mands and your own body actions and sounds. Command the do15．下列命题中，正确的是（　　）A．平行四边形的对角线相等B．矩形的对角线互相垂直C．菱形的对角线互相垂直且平分D．对角线相等的四边形是正方形