During the secretory phase of the menstrual cycle
a. progesterone levels are at their highest
b. lh reaches its highest levels
c. estrogen reaches its highest levels
d. the graafian follicle forms 1 points

Option A.

Explanation:

Secretory phase in menstrual cycle is the second half after ovulation.

During the secretory phase, the corpus luteum secretes high level of progesterone that prepares the endometrium wall for  implantation of an embryo and if fertilization does not take place, it results in menstrual flow.

Hence, the high level of progesterone takes place during secretory phase of menstrual cycle.