Someone with a heart of gold is a genuinely kind and caring person. They would do anything for you.
My Mum has a heart of gold. She always thinks of others before herself.
John offered to do all the decorating this weekend; he's got a heart of gold.
If someone has a heart of stone they are the opposite of someone with a heart of gold; they are unkind and cruel.
You'll get no sympathy from the boss. He has a heart of stone.
The sea otter is a marine mammal that lives on the coasts of the northern and eastern North Pacific Ocean (although the one in this photo is in a zoo in Tokyo). It dives to the sea floor to look for food. It eats mostly shellfish and some kinds of fish.