Figure 1 shows the variation in the level of progesterone during a typical 28-day menstrual cycle.
Which of the following is the maximum concentration of progesterone reached during this cycle?
2 nmol L−12\text{ nmol L}^{-1}2 nmol L−1
21 nmol L−121\text{ nmol L}^{-1}21 nmol L−1
45 nmol L−145\text{ nmol L}^{-1}45 nmol L−1
60 nmol L−160\text{ nmol L}^{-1}60 nmol L−1
