What Is the Principal Disadvantage of Mixed Methods Research

What is the principal disadvantage of mixed methods research?

A) Its results are impossible to integrate, so interpretation is highly subjective.
B) Because of its complexity, researchers from different research traditions must be called upon to collaborate, in order to conduct the study.
C) The time required to complete a mixed methods study is more than that which would be required for completing one that utilizes only one method.
D) Quantitative data usually are converted to qualitative data before analysis or interpretation, so that a cohesive analysis can be accomplished.