Which of the following statements about the Moon is true?
A) The Moon goes through a cycle of phases because it always has the same side facing Earth.
B) If you see a full Moon from North America, someone in South America would see a new Moon.
C) The Moon's distance from Earth varies during its orbit.
D) The Moon is visible only at night.
E) The side of the Moon facing away from Earth is in perpetual darkness.
Question 2
In very general terms, how do the temperature structures of the atmospheres of Venus and Mars differ from that of Earth?
A) They lack X-ray absorbing thermospheres.
B) They lack ultraviolet-absorbing stratospheres.
C) Their atmospheres are similar in structure to Earth's, but with much higher temperatures.
D) Temperatures in their tropospheres increase with altitude, rather than decreasing with altitude.
Gametic life cycle, as illustrated by diatoms
Stages of the asexual cell cycle
The Moon passing in front of the Sun, from the STEREO-B spacecraft.
Cori cycle
HIV cycle in an infected cell: (a) latent infection; (b) active infection.
Anterosuperior view of true pelvis (blue)