Which bonds are used primarily for capital investment in airports by private entities?

The correct choice is Industrial Development Bonds. These bonds are specifically designed to finance the construction and improvement of facilities that will generate economic development, which includes investments in airport infrastructure. Private entities can issue these bonds to attract funding for capital-intensive projects, as they often provide a tax-exempt status that makes them appealing to investors.

Industrial Development Bonds enable private companies to finance airports and related facilities without imposing the same financial burden on the public sector. This is particularly beneficial for projects that may not be funded through typical public finance methods. The focus of these bonds is to stimulate economic growth, thus making them particularly suited for capital investment in airports.

The other options, while related to financing, serve different purposes. General obligation bonds are typically issued by governments and are backed by the full faith and credit of the issuer, thus they don't specifically target private entities. Hybrid bonds may combine features of various bond types but are not specifically focused on capital investment for airports. Special facility bonds are aimed at funding specific facilities with dedicated revenues but may not be as widely used or applicable to all scenarios involving private investment in airports.