Option 1: If the equatorial plane of the earth is not inclined to its orbit, the duration of the year would not be longer. The duration of the year is determined by the time it takes for the earth to complete one orbit around the sun, which is approximately 365.25 days. The inclination of the equatorial plane does not affect this duration.

Option 2: If the equatorial plane of the earth is not inclined to its orbit, it does not necessarily mean that summer would be warmer. The temperature during summer is influenced by various factors, including the tilt of the earth`s axis and the amount of sunlight received in a particular hemisphere. The inclination of the equatorial plane does not directly determine the temperature during summer.

Option 3: If the equatorial plane of the earth is not inclined to its orbit, there would indeed be no change of seasons. The seasons are caused by the tilt of the earth`s axis, which causes different hemispheres to receive varying amounts of sunlight during different times of the year. Without this tilt, the distribution of sunlight would be relatively consistent throughout the year, leading to no distinct seasons.

Option 4: If the equatorial plane of the earth is not inclined to its orbit, it does not necessarily mean that