Final answer:
The Leatherback sea turtle got its name because its species was uncertain at the time it was discovered. It is part of the Testudines order and is the largest sea turtle species. Option 5.
Step-by-step explanation:
The seven sea turtles include the Loggerhead, Green, Hawksbill, Kemp's Ridley, Leatherback, Olive Ridley, and Flatback turtles.
The Leatherback turtle was named so because its species was uncertain when it was first encountered.
The Leatherback turtle (Dermochelys coriacea) is the largest sea turtle, capable of reaching up to seven feet in length and weighing over 2,000 pounds.
In contrast, the smallest turtle is the speckled padloper tortoise, measuring just three inches in length. Turtles, including sea turtles, are characterized by their shell, which can be either bony or cartilaginous and develops from their ribs.
All sea turtles are members of the Testudines order, a group of reptiles that appeared approximately 200 million years ago.
Hence, the right answer is option 5.