All whole numbers are natural numbers. true or false? explain.

It depends on which definition of 'whole numbers' you use. 
Some definitions say the whole numbers are the set of positive integers including zero; or the set of all non-negative integers. In this case, the answer would be 'false', since the set of integers includes negatives. 
However, if you are using a definition of whole numbers which includes positive integers, including zero, and their negatives, the answer would be 'true'. Figure out how the term 'whole numbers' is being defined, then you can get your answer.  

Hope this helped you. :)