Which of the following layers of the Earth is unique among the terrestrial planets?
A) hydrosphere
B) ionosphere
C) mantle
D) crust
E) core
Question 2
What are constellations?
A) groups of galaxies gravitationally bound and close together in the sky
B) groups of stars making an apparent pattern in the celestial sphere
C) groups of stars gravitationally bound and appearing close together in the sky
D) ancient story boards, useless to modern astronomers
E) apparent groupings of stars and planets visible on a given evening
The geological timescale and an overview of the history of life on Earth
The Sun is the nearest star to Earth.
Animation of the apparent retrograde motion of Mars in 2003 as seen from Earth
Earth and the Moon
Layers of the GI Tract
Neurons in the outer layers of the brain