Choose the best answer.

1		Comets ________________.
			A)	follow orbits around the earth
			B)	follow orbits around the sun
			C)	move randomly through the solar system
			D)	are the tracks left in the atmosphere by meteoroids
2		The majority of meteoroids consist of _________________.
			A)	silicate minerals
			B)	calcite
			C)	iron
			D)	nickel
3		The planets shine because they _________________.
			A)	emit light
			B)	reflect sunlight
			C)	reflect moonlight
			D)	reflect starlight
4		The orbits of all planets lie nearly in the same plane except for that of __________________.
			A)	Venus
			B)	Uranus
			C)	Mars
			D)	Pluto
5		The smallest of the following planets is _________________.
			A)	Mars
			B)	Jupiter
			C)	Saturn
			D)	Uranus
6		The largest of the following planets is _________________.
			A)	Mars
			B)	Jupiter
			C)	Saturn
			D)	Uranus
7		The length of the year is shortest on __________________.
			A)	Mercury
			B)	Venus
			C)	Earth
			D)	Pluto
8		The planet that appear brightest in the sky is _______________.
			A)	Venus
			B)	Mars
			C)	Jupiter
			D)	Saturn
9		The largest of Jupiter's satellites is about the size of _______________.
			A)	a large ship
			B)	the moon
			C)	Mercury
			D)	the earth
10		Compared with the earth, Mars has _________________.
			A)	a denser atmosphere
			B)	more surface water
			C)	a lower average surface temperature
			D)	a shorter year
11		The rings of Saturn _________________.
			A)	are gas clouds
			B)	are sheets of liquid
			C)	are sheets of rock
			D)	consist of separate particles
12		Most asteroids lie in a belt between _________________.
			A)	mercury and the sun
			B)	Earth and Mars
			C)	Earth and the moon
			D)	Mars and Jupiter
13		Relative to the time the moon take to circle the earth, the period of its rotation on its axis is ___________________.
			A)	shorter
			B)	the same
			C)	longer
			D)	any of the above, depending on the time of the year
14		The moon's diameter is about __________________.
			A)	1/10 that of earth
			B)	1/4 that of earth
			C)	1/2 that of earth
			D)	3/4 that of earth
15		Eclipses of the sun occur at __________________.
			A)	new moon
			B)	first or last quarter
			C)	full moon
			D)	anytime
16		An eclipse of the moon occurs when the ___________________.
			A)	moon passes directly between the earth and the sun
			B)	sun passes directly between the earth and the moon
			C)	earth passes directly between the sun and the moon
			D)	moon's dark side faces the earth
17		The moon's maria are _________________.
			A)	bodies of water like the earth's oceans
			B)	solid lava flows
			C)	lava flows pulverized by meteoroid impacts
			D)	hardened sediments
18		Most of the craters on the moon are probably the result of __________________.
			A)	volcanic action
			B)	meteoroid bombardment
			C)	erosion
			D)	collisions with asteroids
19		The time needed for the Apollo spacecraft to reach the moon was about ________________.
			A)	3 h
			B)	3 days
			C)	3 weeks
			D)	3 months
20		Relative to the oldest rocks that have been found on the earth, the oldest known lunar rocks are _________________.
			A)	very much younger
			B)	somewhat younger
			C)	about the same age
			D)	older