已知圆的极坐标方程ρ=2cosθ，直线的极坐标方程为ρcosθ﹣2ρsinθ+7=0，则圆心到直线距离为____
阅读下面的一段话，判断正误。
Hi! I'm John. Come here, my friends! Look at my dog. It has two big eyes. It's very cute. This is my cat, Mimi. It's fat. It's two years old. I have six fish. Oh! Mimi likes(喜欢) my fish. I have a bird, Polly. It's beautiful!
某学习小组用KClO3和MnO2的混合物加热制取O2，收集到4.8gO2后停止加热，称得剩余固体的质量为28.0g，继续加热至不再产生O2，最终剩余固体质量为23.2g，试计算（不考虑O2的损耗）；
写出反义词。
好奇—____ 未知—____ 止步—____
