Quantitative researchers seek to ensure that their findings can be applied to other groups and settings. what is this called?

This is known as external validity. 

External validity refers to the extent to which findings from a research study can be extrapolated or generalized to people who were not part of the study, or to the population in general. In quantitative research, generalizability or external validity of a study serves as a quality check when assessing the value of a study. 

B) .. change at different rates to different degrees