Which Statement Is Not True About Nonresponse Issues in Sampling

Which statement is not true about nonresponse issues in sampling?

A) Increasing the response rate may not reduce nonresponse bias.
B) Nonresponse error is one of the most significant problems in survey research.
C) Response rates themselves do not indicate whether the respondents are representative of the original sample.
D) For a given study, if the nonrespondents differ from the respondents on the characteristics of interests, the sample estimates will only be mildly biased.