Why Do Neither Matched Samples nor Matched Pairs Effectively Eliminate

Multiple Choice

Why do neither matched samples nor matched pairs effectively eliminate the possibility of a third-variable correlation?

A) Each technique depends on the other;matched samples are studied first,followed later by matched pairs.
B) Both techniques allow us to rule out a particular third variable as a causal agent,but not the possibility of other third variables.
C) Both techniques fail to utilize random sampling.
D) By eliminating specific third variables,cause-and-effect relations are artificially established.