Which is the largest living species of tortoise in the world, which may weight about 400 kg?

Option D

The Galápagos tortoise complex or Galápagos giant tortoise complex (Chelonoidis nigra and related species) are the largest living species of tortoise. Modern Galápagos tortoises can weigh up to 417 kg (919 lb). Today, giant tortoises exist on only two remote archipelagos: the Galápagos Islands 1000 km due west of mainland Ecuador; and Aldabrachelys gigantea of Aldabra in the Indian Ocean, 700 km east of Tanzania.

The Galápagos tortoises are native to seven of the Galápagos Islands, a volcanic archipelago about 1,000 km (620 mi) west of the Ecuadorian mainland. With lifespans in the wild of over 100 years, it is one of the longest-lived vertebrates. A captive individual lived at least 170 years. Spanish explorers, who discovered the islands in the 16th century, named them after the Spanish galápago, meaning "tortoise".

Shell size and shape vary between populations. On islands with humid highlands, the tortoises are larger, with domed shells and short necks; on islands with dry lowlands, the tortoises are smaller, with "saddleback" shells and long necks. Charles Darwin's observations of these differences on the second voyage of the Beagle in 1835, contributed to the development of his theory of evolution