ACT reading practice test 20

DIRECTIONS: Each passage is followed by several questions. After reading a passage, choose the best answer to each question and fill in the corresponding oval on your answer document. You may refer to the passages as often as necessary.


NATURAL SCIENCE: This passage is adapted from "A Comment on Comets" by Dr. Anatole C. Thierry (? 2002 by Weak Alliteration Press).

1. The primary purpose of the passage is to:

A. persuade readers that astronomers have not yet done adequate studies to discover the origins of the solar system.
B. encourage readers to learn to use telescopic equipment to aid in the search for new comets.
C. describe the characteristics of comets currently known by astronomers and the motivation for their research.
D. catalogue the experiments planetary scientists have done to determine the composition of comets.

2. The author would most likely agree with which of the following statements?

F. There may be minerals in the solar system yet to be discovered by astronomers.
G. Astronomers will not be able to observe comets brighter than IRAS-Araki-Alcock because their orbital periods are so long.
H. Comets are older than the Earth as indicated by their greater distance from the Sun.
J. Collections of samples directly from the surface of comets will be difficult because of comets' unpredictability.

3. According to the passage, which situation creates a comet's maximum brightness as observed from Earth?

A. Its coma is much bigger than its nucleus.
B. It is closer to the Earth and therefore moves more quickly.
C. Its perihelion occurs after it passes the Earth.
D. It is at its closest to the Earth after its perihelion.

4. Which of the following questions is NOT answered by information given in the passage?

F. What do astronomers hope to learn by studying comets?
G. What causes some comets to be trailed by such a long tail?
H. What prevents astronomers from cataloging more new comets and predicting their approach to the Earth?
J. Why do comets have such a highly eccentric orbit?

5. Information in the first paragraph indicates that "the appearance of comets" requires all of the following EXCEPT:

A. the viewer to have a powerful telescope.
B. solar winds and radiation pressure to scatter the coma.
C. a portion of the surface material to evaporate.
D. an envelope of gas and dust much larger than the nucleus.

6. The passage mentions astronomers observing all of the following about comets EXCEPT:

F. unusual minerals in the chemical composition that have not been found on Earth.
G. comets that emit bright light from their nuclei.
H. changes in apparent brightness at different times and in different environments.
J. orbits that take comets to the edges of the Sun's gravitational influence.

7. In the context of the third paragraph (lines 29-48), lines 34-38 primarily serve to emphasize the:

A. relationship a comet's apparent speed has to its other visual characteristics, such as its apparent diameter.
B. influence a comet's distance from Earth with regard to its perihelion has on a comet's apparent brightness.
C. disappointment astronomers feel when highly anticipated celestial events do not live up to their expectations.
D. difficulty in predicting when comets will be visible in the sky because of their highly eccentric orbits.

8. The passage most nearly indicates that attempts to study comets directly have been:

F. prevented by technical difficulties.
G. used to explain life on Earth.
H. unsuccessful so far.
J. promising, but incomplete.

9. As it is used in line 55, the phrase "characteristics beyond the novelty of these comets" most likely refers to:

A. the likelihood of discovering new comets.
B. the difficulty of detecting distant comets.
C. comets' chemical composition.
D. the age of comets.

10. The main purpose of the last paragraph is to:

F. describe particular experiments that have been performed on comets as they pass near the Earth.
G. convince readers that comets are responsible for the evolution of intelligent species.
H. discuss the reasons planetary scientists are interested in pursuing direct study of comet material.
J. contradict outdated information about the origin of the solar system.