Q. A bond whose proceeds are used only to finance or refinance a combination of both environmental and social projects is called:
(a) Green Bond
(b) Social Bond
(c) Sustainability Bond
(d) Sovereign Bond

Answer : C

Explanation:

Sustainability Bond — proceeds used to finance a combination of both environmental and social projects
Green Bond — proceeds used exclusively for environmental/climate projects
Social Bond — proceeds used exclusively for social projects (healthcare, education, affordable housing, etc.)
Sovereign Bond — a government-issued debt instrument with no restriction on end-use of proceeds

Source:

https://www.pimco.com/gbl/en/resources/education/understanding-green-social-and-sustainability-bonds