Questions

From the given options, Though is the only word which gives sense for the sentence. Hence, Though pompous he was an entertaining person.

Mixed heart means the heart in which the oxygenated and the deoxygenated blood is mixed. Reptiles and amphibians have mixed heart.

The Olive ridley turtles are the smallest and most abundant of all sea turtles found in the world, inhabiting warm waters of the Pacific, Atlantic and Indian oceans. These turtles, along with their cousin the Kemps ridley turtle, are best known for their unique mass nesting called Arribada, where thousands of females come together on the same beach to lay eggs. Though found in abundance, their numbers have been declining over the past few years, and the species is recognized as Vulnerable by the IUCN Red list.The coast of Orissa in India is the largest mass nesting site for the Olive-ridley, followed by the coasts of Mexico and Costa Rica.

Here from the above options, Algae is an Autotroph.

Autotrophs : 

An Autotroph is also called as Producer, is an organism that produces complex organic compounds from simple substances present in its surroundings, generally using energy from light or inorganic chemical reactions.