Answer:
the answer is Z,X,W,Y
Step-by-step explanation:
we know Z is the hardest material because when it is rubbed against any material,the other material is definitely left with a mark,so Z is 1st
we know Y is the weakest material because when it is scratched by all other materials,it is left with a mark.so we write Y at the last.
X is rubbed against W and W is left with a mark,so we know that X is harder than W,so we should write X just before W and after Z.