I'm trying to create a selectbox where when you select certain options in the selectbox, it automatically selects a group of options in the same selectbox. So lets say we had a selectbox with these options:

 

fruit

apple

banana

pear

animals

monkey

elephant

kangaroo

 

I would like to make it to where if the user selected "fruit" as an option, apple, banana and pear would automatically get selected also and if htey chose "animals", all the animals would also get selected. Any ideas?