The sun's declination is 0° at the a. summer and winter solstice b. summer and winter equinox c. vernal and autumnal solstice d. vernal and autumnal equinox

-- "Declination zero" means the object is in the sky at some point directly over the Earth's equator.  

-- If it's the sun and it appears to be over the equator, then that tells us that the Earth's axis is not tilted toward or away from it.  

-- That in turn tells us that the Earth is at one of the two equinoxes in its orbit, either the Spring one or the Autumn one. (D)

-- (The first days of Summer and Winter coincide with solstices, not equinoxes.)  

The sun's declination is 0 degrees at the vernal and autumnal equinox hopefully this helps!

as we probably am aware that our atmosphere or air have various levels, each level has different gasses, and each gas has another porousness. at the point when the light originates from lower porousness to higher penetrability, it alters its course. with the goal that implies that when the light originates from the moon to the earth, it alters it's course a lot more occasions. it essentially implies that the state of the light piece of the moon is changed on the earth.

not copied too! hope this !

joke:

h o h o hope you have a merry christmas!