Which of the following statements are true?

i. the area under a normal curve is always equal to 1, no matter what the mean and standard deviation are.
ii. the smaller the standard deviation of a normal curve is, the higher and narrower the graph.
iii. normal curves with different means are centered around different numbers.

a. i and ii
b. i and iii
c. ii and iii
d. i, ii, and iii
e. none of the above