Answer:a) a sturdy-finned, shallow-water lobe-fin whose appendages had skeletal supports similar to those of terrestrial vertebrates.
Explanation:
An ancestor - An earlier type of a species at any distant time — a progenitor.
A tetrapod is any vertebrate with four limbs. It includes any vertebrate (such as birds or snakes) that have evolved from early tetrapods — especially all members of the superclass Tetrapoda.
The presence of bones that support the appendages in Lobe – fin fish were found to be similar to the categorical skeletal supports found in the limbs of sample tetrapods. The sub class crossopterygii includes the Lobe – fin fish, which is seen as one of the recent common ancestor of living tetrapod today.
The making of replicas of the original fossils, is pretty much the say way, just different materials, in which the fossils originally have been formed and preserved.
When an organism dies, be it a plant or an animal, it gets fossilized only if very quickly after the death it is covered with sediments or mud. The sediments or the mud protect the plant or animal from the outside influences, so once it is kind of in a vacuum, or protective layer if you will, in which parts of the plant or animal that are long-lasting are preserved.
The clay and plaster used for the replica, work in the same way, because they wrap around the fossil tightly and isolate it from outside influences, with the result being different though, as they just make a copy of the fossil.
I think its the Diurnal Cycle.
