Final answer:
The seasons are determined by the tilt of the Earth's axis as it orbits the Sun, with option a) defining the correct months associated with each season in the Northern Hemisphere.
Step-by-step explanation:
To determine the season based on a given month and day, you can use astronomical events like equinoxes and solstices that mark the transition points between the seasons. In the process of the Earth's orbit around the Sun, the Northern and Southern Hemispheres tilt towards or away from the Sun, which results in varying lengths of day and directness of sunlight, thus leading to seasons. The correct formula for the seasons, assuming we're discussing the Northern Hemisphere, is option a) Spring = March to May, Summer = June to August, Fall = September to November, Winter = December to February.
For example, summer in the Northern Hemisphere starts with the summer solstice, around June 21, when Earth's axis tilts the Northern Hemisphere towards the Sun resulting in the longest day of the year. Conversely, winter begins around December 21 with the winter solstice, when the Northern Hemisphere is tilted away from the Sun, giving us the shortest day of the year. Equinoxes, occurring around March 21 and September 23, signal the beginning of spring and fall respectively, with day and night being of approximately equal length.