Astudy is conducted on the possible relationship between blood pressure and hemoglobin a1c

Taking into account that the question to this statement is: Which numerical measure is appropriate? The answer is:

Standard deviation  

five-summary  

(correlation coefficient) # between -1 and 1 calculated so as to represent the linear dependence of two variables or sets of data.

Conditional percentages.

*Standard deviation is defined as a quantity expressing the difference between group members and the mean value of the group .

answer; the above is true;

is there any answer choices to this?