Consider the following statements about elephants :

A. Elephants do not rest very much, they sleep 2 to 4 hours only in a day.

B. An adult elephant can eat more than 200 kg of leaves and twigs in a day.

C. They love to play with mud and water, the mud keeps their skin cool.

D. In elephant herd the oldest female elephant decides everything.

The correct statements are

The correct option is C, D and A.

Let us analyze each statement given about elephants:

Statement A: "Elephants do not rest very much, they sleep 2 to 4 hours only in a day."
This statement is correct. Elephants spend very little time sleeping, usually between 2 to 4 hours in a day.

Statement B: "An adult elephant can eat more than 200 kg of leaves and twigs in a day."
This statement is incorrect. An adult elephant can eat up to 100 kg (not 200 kg) of leaves and twigs in a single day.

Statement C: "They love to play with mud and water, the mud keeps their skin cool."
This statement is correct. Elephants enjoy playing in water and mud because mud helps to keep their skin cool and protects it from the heat and sun.

Statement D: "In elephant herd the oldest female elephant decides everything."
This statement is correct. An elephant herd is matriarchal, which means the oldest female elephant acts as the leader and makes decisions for the herd.

Therefore, statements A, C, and D are correct, making C, D and A the correct option.