4. The author of the passage probably mentions Canizares' determination in order to

　　(A) clarify an ambiguity in Fabian's research findings

　　(B) illustrate a generalization about the temperature of gas in a galaxy cluster

　　(C) introduce a new argument in support of the orthodox view of galaxies

　　(D) provide support for Fabian's assertions about the Perseus galaxies

　　(E) provide an alternate point of view concerning the movement of gas within a galaxy cluster

　　5. According to the passage, Fabian believes that gas flowing into a central galaxy has which of the following characteristics?

　　(A) It is one-tenth hotter than it was in the outer regions of the galaxy cluster.

　　(B) It emits radiation with wavelengths that change as the gas moves toward the center of the galaxy.
　(C) The total amount of radiation emitted diminishes as the gas cools.

　　(D) It loses 90 percent of its energy as it moves to the center of the galaxy.

　　(E) It condenses at a rate much slower than the rate of decrease in temperature as the gas flows inward.

　　6. According to the passage, Fabian's theory makes use of which of the following principles?

　　(A) Gas emanating from an explosion will be hotter the more distant it is from the origin.

　　(B) The wavelength of radiation emitted by a gas as it cools remains constant.

　　(C) If pressure remains constant, the volume of a gas will decrease as it is cooled.

　　(D) The volume of a gas will increase as the pressure increases.

　　(E) As gas cools, its density decreases.

　　7. It can be inferred from the passage that which of the following is true of Fabian's theory?

　　(A) It did not receive approval until Canizares' work was published.

　　(B) It was not widely accepted in the 1970's.

　　(C) It did not receive support initially because technology was not available to confirm its tenets.

　　(D) It supports earlier speculation that intergalactic gas was largely the result of explosions outside the galaxy.

　　(E) It was widely challenged until x-ray evidence of gas temperatures in NGC 1275 had been presented.