Final answer:
The inclination of Earth's axis in relation to its orbit around the Sun is called obliquity. Earth's axis is currently tilted at about 23.5°, leading to the seasons. Precession, a different concept, refers to the Earth's axis's slow wobble in a 26,000-year cycle.
The correct option is b.
Step-by-step explanation:
The inclination of Earth's axis in relation to its plane of orbit around the Sun is known as obliquity. Obliquity refers to the tilt of the Earth's rotational axis away from a perpendicular position relative to the orbital plane. The Earth's axis is currently tilted at about 23.5°, and this tilt is responsible for the changing seasons. Unlike obliquity, precession is the slow conical motion of the Earth's axis of rotation. Caused mainly by the gravitational pull of the Moon and Sun on the equatorial bulge, Earth's precession has a cycle of approximately 26,000 years, during which the direction in the sky to which Earth's axis points goes around a big circle. This precessional movement is similar to the motion of a spinning top, and it affects the timing of the seasons by changing the point during Earth's orbit when each hemisphere is tilted toward the Sun.