wag its tail

The robotic cat can wag its tail.(那只机器猫能摇尾巴。)

The dog gave a wag of its tail.(那条狗摆了摆尾巴。)

When a dog is happy, it will wag its tail.(狗狗高兴的时候会摇尾巴。)

Every time I go home, it will wag its tail to me.(每次我回到家，它就会朝我摇尾巴。)

You can buy a pretty good dog with a lot of money, but you can't buy the wag of its tail.(你可以花大笔钱买一条漂亮的狗，可是你买不到狗儿摇动的尾巴。)

It is as though instead of a dog wagging its tail the tail should wag the dog.(这情况恰似尾巴倒过来摇狗而不是狗摇尾巴了。)

Well, then, 'the Cat went on,' you see, a dog growls when it's angry, and wags its tail when it's pleased. Now I growl when I'm pleased, and wag my tail when I'm angry.(“好，那么，”猫接着说，“你知道，狗生气时就叫，高兴时就摇尾巴，可是我，却是高兴时就叫，生气时就摇尾巴。”)

Money will buy you a fine dog, but only love can make it wag its tail.(有钱就能买只可爱的狗，但是有爱才能让它对你摇尾巴。)

Why does a dog wag its tail?(狗为什么要摇尾巴？)