Khan academy

After a certain medicine is injected, its concentration in the bloodstream changes exponentially
over time.
The graph describes the medicine's concentration (in milligrams per liter) over time (in hours).
concentration
(mg/l)
100
90-
80-
70-
60
50-
40-
30-
20-
10.
←
1 2 3
4
5 6 7
time
(hours)
How does the medicine's concentration change over time?
A?
B?
C?
D?