A student claims, "In humans, ovulation always happens on day 14 of the menstrual cycle." Critically examine this claim and state whether the claim is correct or not. Give at least two reasons for your answer.

The claim is not completely correct. Ovulation does not always occur on day 14 of the menstrual cycle. Day 14 is only an approximate value for a menstrual cycle of about 28 days. Firstly, the length of the menstrual cycle differs from person to person. Some women may have shorter or longer cycles, so the timing of ovulation also changes accordingly. In longer cycles, ovulation may occur later, while in shorter cycles it may occur earlier. Secondly, the timing of ovulation can vary due to factors such as stress, illness, hormonal changes, diet, and overall health. Even in the same person, ovulation may not occur on exactly the same day every month.
Therefore, it is more accurate to say that ovulation usually occurs around the middle of the menstrual cycle rather than always on day 14.