Your question should be 'What does 'cross section' mean?' and you asked this same question 10 days ago?
Have you forgotten this already? Or did you not believe the answers you were given?
Here is your question:
and here's the answer I gave you:
A cross section has examples from all classes.
'Section' is a cut, and 'cross' means 'across'. Imagine you have a gateau made in layers, with cake, chocolate, cream, fruit and so on, one layer on top of the other. If you take a bit from the top, you'll only get what's on the top layer, won't you? But if you take a knife and across the cake, the slice you take out will have a sample of all the layers that the cake is made up of. That's what a 'cross section' is.