The main way in which Western financial institutions invest in equity investment funds is ( ).

In Western countries, financial institutions involved in equity investment funds mainly include commercial banks and investment banks. Financial institutions invest in equity investment funds mainly in two ways: ① as a fund investor invested in equity investment funds; ② as a fund manager initiated the establishment of funds, directly involved in equity investment. Large enterprises with financial strength usually take two ways to participate in equity investment. ① their own capital, in the form of subsidiaries for venture capital or mergers and acquisitions investment business; ② as an investor, to participate in the professional fund 1 manager initiated the establishment of equity investment funds. Therefore, D is correct.