Author Question: When Earth was young, its atmosphere had no free ____. a. nitrogen b. oxygen c. helium d. carbon ... (Read 73 times)

fbq8i · **on:** Jul 27, 2018

When Earth was young, its atmosphere had no free ____.

a. nitrogen
b. oxygen
c. helium
d. carbon dioxide
e. water vapor

Question 2

As a star like the Sun exhausts hydrogen in its core, the outer layers of the star become hotter and more luminous.

a. True
b. False
Indicate whether the statement is true or false