Hinderburg on Adani Group

Current context: Hinderburg Research, a financial research company, has released a report on the world's third-richest man and his business firm, the Adani Group.

• The report alleges that Adani was involved in fraudulent and "brazen" stock manipulation. The report is based on two years of investigation into Adani and his family members.
•  According to the report, the Adani Group manipulated 218 billion USD in stocks, with Adani's net worth at 120 billion USD, largely accumulated through stock price appreciation.
• Seven Adani companies saw a spike of 819% in the last three years, but the report states that these companies are actually in debt and facing liquidity pressure.
• The report also alleges that Rajesh Adani, Gautam's younger brother, was twice arrested and accused of creating shell companies abroad and importing and exporting diamonds fraudulently.
• The Adani family's shell companies in the UAE, Maldives, and Caribbean Islands earned them a profit of 17 billion USD through tax-haven jurisdictions.
• The report also alleges that Vinod Adani, Gautam's elder brother, is said to own and operate entities in Singapore and the UAE. Still, Hindenburg Research claims there are no operations in these entities.

Question: 

Q.1 Who released a research report on the Adani Group recently?
a.SBI
b.RBI
c.Hinderburg
d.Billionaire index organisation