How debentures can be issued by the company?

The correct answer is option 3- Both of these.

Debenture can be issued through private placement & public issue.

A company raises its capital by means of issue of shares. But the funds raised by the issue of shares are seldom adequate to meet their long term financial needs of a company. Hence, most companies turn to raising long-term funds also through debentures which are issued either through the route of private placement or by offering the same to the public.