This is a statement that is always true, forwards and backwards.
a) axiom b) definition c) postulate d) theorem

B) Definition is a statement that is always true forwards and backward.

Step-by-step explanation:

A definition is a statement which tells the meaning of the term. So, it has two parts 1)-term and 2)meaning of term. We can write it forward and backward.

For example:- We are writing definition of equality then we say " Equality is  the state of a group of people of being equal in rights and status."

If we write it in backward then we can write

" The state of a group of people of being equal in rights and status is called equality."

Therefore definition is a statement is always true forward and backward.