SEM Which company is the best?

I know more about Zibolan and Adsage in Beijing. These are some old SEM companies, and their services, technologies and tools are up to standard. They specialize in SEM and make a living from it. They are all professionals. Others were established only in the last two years, lacking relevant technology and experience. Some rely on selling advertisements from other media and don't pay attention to this piece. You have to look at people. For delivery and optimization, you need an excellent optimizer. Now the well-known are all famous for training. They earn money by training, and they speculate with each other. If they do, it won't work.