There is an angle between the ecliptic and the celestial equator because a. Earth's axis is tilted with respect to its orbit. b. Earth's orbit is tilted with respect to the orbits of other planets. c. the Sun follows a rising and falling path through space. d. the Sun's orbit is tilted with respect to Earth's.

The ecliptic is a fundamental concept in astronomy and is crucial to understanding Earth's movements relative to the Sun. Think of the ecliptic as the Sun's annual path through the sky. It represents the plane of Earth's orbit around the Sun.
This imaginary line is due to the Earth's year-long journey around the Sun, and we see it as the Sun's apparent motion.
Understanding the ecliptic helps explain the changing positions of the Sun, Moon, and planets through the zodiac constellations.
One useful way to visualize the ecliptic is by imagining a flat disk that the Earth sits in the middle of, spinning around the Sun.

The celestial equator is another important imaginary line in the sky. It is simply Earth's equator extended out into space.
If you imagine Earth as a giant sphere, then the celestial equator is what you get when you draw an imaginary line from Earth's equator straight out into the cosmos.
It divides the sky into northern and southern hemispheres, similar to how Earth's equator divides the planet.
When observing the stars and planets, the celestial equator helps us understand their positions in the sky relative to our location on Earth.

The orbital plane is the flat, disk-shaped space in which Earth orbits the Sun. It can be thought of as the 'floor' of Earth's path around the Sun.
Imagine it as a large, flat surface stretching out from the Earth's orbit, containing the paths of other planetary bodies in our solar system.
This plane is crucial for comprehending why we see the Sun, Moon, and planets move the way they do in our sky.
Earth's axial tilt, which is about 23.5 degrees, causes Earth's equatorial plane to not align perfectly with the orbital plane. Hence, the celestial equator is angled relative to the ecliptic.
It is this tilt that causes the seasons and the varied path of the Sun across the sky throughout the year.