Which of the following must be used to make a recommendation credible?

A) Primary data
B) Knowledge management systems
C) Logical analysis and sound conclusions
D) Statistical analysis
E) Correlations between the recommendation and the data

Logical analysis and sound conclusions must be used to make a recommendation credible. While primary data, knowledge management systems, statistical analysis, and correlations between the recommendation and the data can all be helpful in supporting a recommendation, it is the logical analysis and sound conclusions that ultimately determine its credibility.