Explanation:

According to researchers from the Indian Institute of Science, the Indian Ocean harbors a colossal and enigmatic phenomenon known as the "Gravity Hole," may be the remnants of an ancient sea that vanished millions of years ago.

• The gravity hole is a region of the ocean where the effects of gravity are less than usual.

• It occurs at the bottom of the ocean where there are gravitational anomalies.

Why it occurs?

• These anomalies are caused by variations in the gravitational pull of the Earth due to differences in the density of the materials that make up the Earth’s crust.

• The Indian Ocean is home to one of the most profound gravitational anomalies on Earth known as the Indian Ocean Geoid Low (IOGL).

• It was discovered in 1948 during a ship-based gravity survey by Dutch geophysicist Felix Andries Vening Meinesz.

• It is found in a large section of over three million sq. km in the Indian Ocean seafloor, located around 1,200 km southwest of India’s southern tip.

•  It is estimated to have formed approximately 20 million years ago.

• Researchers said that the IOGL comprises slabs from the Tethys Ocean, a long-lost sea that plunged into the depths of the planet millions of years ago. 

• The Tethys Ocean, which once separated the supercontinents of Gondwana and Laurasia is believed to have perturbed the African Large Low Shear Velocity province

Hence only statement 2nd is correct.