[单项选择]The discussion of the means by which GHBs escape black holes that is offered in the second paragraph suggests that which of the following must be assumed if the conclusions described in lines 3 - 5 are to he validly drawn
A. (A) The light emissions from GHBs always degrade from gamma rays to x-rays to visible light and, finally, to radio waves.
B. (B) Particles in GHBs include not only photons but electrons and their antimatter counterpart, positrons.
C. (C) The expansion of a fireball as it moves away from the black hole lowers photon density.
D. (D) Shock waves almost always form at the boundary between the fireball and the external medium.
E. (E) The timescale by which we witness astronomical phenomenon is always ruled by the principles of relativity.

[单项选择]Television is one of the means by which these feelings are created and conveyed.
A. 电视是制造和传播这种感觉的媒介之一。
B. 电视是制造和传播这种情绪的媒介之一。
C. 电视是制造和传播这种情绪的意思之一。
D. 电视是创造和传递这种感情的媒介之一。

[单项选择]

The process by means of which human beings arbitrarily make certain things stand for other things many be called the symbolic process.
Everywhere we turn, we see the symbolic process at work. There are (41) things men do or want to do, possess or want to possess, that have not a symbolic value.
Almost all fashionable clothes are (42) symbolic, so is food. We (43) our furniture to serve (44) visible symbols of our taste, wealth, and social position. We often choose our houses (45) the basis of a feeling that it "looks well" to have a "good address." We trade perfectly good cars in for (46) models not always to get better transportation, but to give (47) to the community that we can (48) it.
Such complicated and apparently (49) behavior leads philosophers to ask over and over again, "why can’t human beings (50) simply and naturally."
A. lead
B. devote
C. proceed
D. return

[单项选择]There are means by which the constitution has been______over so long a time to the needs of a changing society.
A. altered
B. changed
C. adapted
D. revised