Answer:
B. the cycle of the Moon through all its phases
Step-by-step explanation:
Months are determined by the cycle of moon through out all its phases. In a year, the moon has different phases as its revolves round the earth and also on its own axis.
The phases of the moon shows how the moon is view from earth. These phases were studied and it was used in determining months on earth. It was observed that between one phase change of the moon as seen on earth, 29 or 30 or 31 days can pass by.