The correct answer is: C. Can be either positive or negative.
A correlation coefficient is a measure of the strength and direction of the linear relationship between two variables. It is a number between -1 and 1, inclusive. A correlation coefficient of 0 indicates no linear relationship between the variables. A correlation coefficient of 1 indicates a perfect positive linear relationship, and a correlation coefficient of -1 indicates a perfect negative linear relationship.
A positive correlation coefficient indicates that the variables tend to move in the same direction. For example, if there is a positive correlation between height and weight, taller people tend to weigh more. A negative correlation coefficient indicates that the variables tend to move in opposite directions. For example, if there is a negative correlation between height and shoe size, taller people tend to have smaller shoe sizes.
The correlation coefficient can be either positive or negative, depending on the nature of the relationship between the variables.