-In This Image, What Is Represented by the Times Labeled

-In this image, what is represented by the times labeled as "A"? (choose all that apply)
i. timing midway between doses of a drug
ii. timing just before the next dose is given
iii. drug level at its highest serum concentration
iv. drug level at its lowest serum concentration

A) i and ii
B) ii and iv
C) i and iii
D) ii and iii