Hard parts the animals to a) live on land b) swim freely c) feed and reproduce d) protect themselves

I believe the correct answer is Option A and Option D

Hard parts such as skin, horns and paws help animals to survive on land and fight against the predators. For example, Rhinos have thick and hard skin which helps rhinos to bear high temperature, predator attacks and other environmental conditions.

Similarly, elephants have a huge body with thick skin which keeps them safe in their zone. Hard parts of body also help animals to fight against diseases as well.