What day is considered to be the first day of a female’s reproductive cycle?
when hormone levels are low and the uterus lining is shed.
when hormone levels are high and the uterus lining is shed.
when hormone levels are low and the ovary releases an egg.
when hormone levels are high and the ovary releases an egg.

Click an item in the list or group of pictures at the bottom of the problem and, holding the button down, drag it into the correct position in the answer box. release your mouse button when the item is place. if you change your mind, drag the item to the trashcan. click the trashcan to clear all your answers. label the following topographic map. click on a label below the map to select it, and then click on the appropriate box on the map to place the label. (increments for contour lines is 50 ft).

Which part of cellular respiration must occur before any of the other steps can occur

Is there any species that went extinct in recent years due to natural causes (not caused by human interaction). if so, what caused it?