A, B, C and D are all exit mechanisms that private equity investment funds can adopt after completing investment projects. Among them, initial public offering (IPO) refers to the initial offering of common stock of the target enterprise in the securities market. After that, the target enterprise will become a listed company and its shares will be publicly traded in the securities market. Private equity investment funds can recover cash by selling their shares. Generally speaking, IPO is considered as the best exit channel with huge capital gains.