As earth travels in its different constellations are visible at different times of the year.
a.

atmosphere

c.

galaxy
b.

orbit

d.

star cluster

select the best answer from the choices provided

a
b
c
d

c-14 is carbon-14, or radiocarbon.   it is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons.

(b) which contains higher levels of vitamin b, oranges or spinach?

explanation:

you can eliminate a, c, and d because they are questions based on opinions.