Final answer:
Spearman rho is the most appropriate correlation coefficient to use when one or both variables are ordinally scaled and the relationship is linear, as it ranks data before calculating the correlation. The correct option is B.
Step-by-step explanation:
When one or both variables are ordinal scaled and a linear relationship is suspected, the most appropriate type of correlation coefficient to use is Spearman rho. This non-parametric measure ranks the data before calculating the correlation coefficient, hence dealing well with ordinal data and non-normal distributions. To calculate Spearman rho, each value is replaced with its rank, and the Pearson correlation coefficient is computed for these ranks.
The Pearson r is best used when both variables are continuous and normally distributed. However, since we're dealing with at least one ordinal variable, Spearman rho will better fit the data's nature.
The Phi and Eta correlation coefficients are used for different types of data relationships, such as nominal with nominal for Phi, and one or more ordinal with an interval/ratio variable for Eta, which does not apply in this scenario.