In Terms of Learning About Generalization Across Participants

In terms of learning about generalization across participants,

A) the researcher can normally be confident that a result found in one sample will generalize to all populations that he or she is interested in.
B) the researcher can usually be confident that a result found in one sample will not generalize beyond the sample that he or she has studied.
C) no sample of research participants can provide definitive information about how a finding will generalize.
D) it is possible to make highly accurate statements about the likelihood of a finding generalizing to all populations.