Paragraph 1

　　The surface of Mars shows a wide range of geologic features, including huge volcanoes-the largest known in the solar system-and extensive impact cratering. Three very large volcanoes are found on the Tharsis bulge, an enormousgeologic area near Mars's equator. Northwest of Tharsis is the largest volcano of all: Olympus Mons, with a height of 25 kilometers and measuring some 700 kilometers in diameter at its base. The three large volcanoes on the Tharsis bulge are a little smaller-a "mere" 18 kilometers high.

　　1、The word "enormous"In the passage is closest in meaning to

　　○Important

　　○Extremely large

　　○Highly unusual

　　○Active

　　2、According to paragraph 1, Olympus Mons differs from volcanoes on the Tharsis bulge in that Olympus

　　Mons

　　○Has more complex geologic features

　　○Shows less impact cratenng

　　○is taller

　　○Was formed at a later time

　　Paragraph 2

　　None of these volcanoes was formed as a result of collisions between plates of the Martian crust-there is no plate motion on Mars. Instead, they are shield volcanoes-volcanoes with broad, sloping slides formed by molten rock. All four show distinctivelava channels and other flow features similar to those found on shield volcanoes on Earth. Images of the Martian surface reveal many hundreds of volcanoes. Most of the largest volcanoes are associated with the Tharsis bulge, but many smaller ones are found in the northern plains.

　　3、The word "distinctive”in the passage is closest in meaning to

　　○Deep

　　○Complex

　　○Characteristic

　　○Ancient

　　4、According to paragraphs 1 and 2, which of the following is NOT true of the shield volcanoes on the Tharsis bulge?

　　They have broad, sloping sides.

　　They are smaller than the largest volcano on Mars.

　　They have channels that resemble the lava channels of volcanoes on Earth.

　　They are over 25 kilometers tall.

　　Paragraph 3

　　The great height of Martian volcanoes is a direct consequence of the planet's low surface gravity. As lava flows and spreads to form a shield volcano, the volcano's eventual height depends on the new mountain's ability to support its own weight. The lower the gravity, the lesser the weight and the greater the height of the mountain. It is no accident that Maxwell Mons on Venus and the Hawaiian shield volcanoes on Earth rise to about the same height (about 10 kilometers) above their respective bases-Earth and Venus have similar surface gravity. Mars's surface gravity is only 40 percent that of Earth, so volcanoes rise roughly2.5 times as high. Are the Martian shield volcanoes still active? Scientists have no direct evidence for recent or ongoing eruptions, but if these volcanoes were active as recently as 100 million, years ago (an estimate of the time of last "eruption based on the extent of impact cratering on their slopes), some of them may still be at least intermittently active. Millions of years, though, may pass between eruptions.

　　5、The word "roughly" closest In meaning to

　　Typically

　　Frequently

　　Actually

　　Approximately

　　6、In paragraph 3, why does the author compare Maxwell Mons on Venus to the Hawaiian shield volcanoes on Earth?

　　To help explain the relationship between surface gravity and volcano height

　　To explain why Mars's surface gravity is only 40 percent of Earth's

　　To point out differences between the surface gravity of Earth and the surface gravity of Venus

　　To argue that there are more similarities than differences between volcanoes on different planets