20. Which is the most appropriate statement?

(a) As stress increased by 1 standard deviation, blood pressure increased by nearly half a standard deviation

(b) As stress increased by 1 standard deviation, age increased by 0.18 of a standard deviation

(c) As age increased by 1 year, blood pressure fell by 0.18 of a standard deviation

(d) As age increased by 1 standard deviation, blood pressure increased by 18%