PIMCO’s Mohamed El-Erian says that it’s good news that countries like China are willing to cut interest rates to spur growth, but that there are major questions about whether that willingness will result in effectiveness. El-Erian tells CNBC that the global economy is slowing, and says that if it continues to do so central banks — including the Federal Reserve — very well may start taking action. That means investors should focus on the types of investments that central banks would be influencing directly. He also says that investors should retain their optionality, because the market “will give you occasion after occasion to pick up good stocks at low prices.”