A: Since Mac OS X, this operating system is linux based.
B: No, here you can find the refence to mac os x’s kernel: http://en.wikipedia.org/wiki/Mac_OS_X
A: “unix-based”, there you have it 
B: unix != linux
A: come on man… dont be so ultra exactly, linux is part of unix family
B: exactly.
based on the assumptions:
- mac os x is based on unix
- linux is based on unix
the statement:
- mac os x is based on linux
is wrong, because is a wrong sillogism.
analogue:
- chimneys smoke
- my grandfather smokes
=> my grandfather is a chimney.
so, if you say that Mac OS X is unix-based, it’s correct, if you say that is linux-based, it’s wrong.
