设$\overrightarrow{b}$是$\overrightarrow{a}$的相反向量，则下列说法错误的是（　　）

 几千年来中国的厨艺最讲究的就是“火候”二字．现在市面上流行如图1所示的新型电饭锅，采用了“聪明火”技术，电脑智能控温、控压，智能化控制食物在不同时间段的温度，以得到最佳的口感和营养，其简化电路如图2甲所示．R₁和R₂均为电热丝，S是自动控制开关．把电饭锅接入220V的电路中，用电饭锅的“聪明火”煮米饭，电饭锅工作时的电流随时间变化的图象如图2乙所示．

   We can not live a modern life without traveling．The fastest way of traveling is by air．With a plane people can travel in one day to places which it took a month or more to get to a hundred years ago．
   Traveling by train is slower than by plane, but people can see the country when they are traveling through．Modern trains have comfortable seats and dinning-cars．They make even the longest journey（旅途） enjoyable．
   Some people prefer to travel by sea when possible．There are large luxury liners（客轮） or river boats．They are not as fast as trains or planes, but traveling by sea is a very pleasant way to spend a holiday．
   Many people like to travel by car．They can make their own timetable．They can travel hundreds of miles or only fifty miles a day, just as their wish．They can stop wherever they want to see something interesting or to enjoy a good meal at a good restaurant, or to spend the night at a hotel．That is why people choose traveling by car for pleasant trips, while they usually take trains or planes for business．

中央电视台2套“开心辞典”栏目中，有一期的题目如图所示，两个天平都平衡，则三个球体的重量等于个正方体的重量(   )