【单选题】Which of the following, if presented as the first sentence of a succeeding paragraph, would most logically continue the discussion presented in the passage?
A.
Timekeeping in medical tomography must be precise because the changes in travel time caused by density fluctuations are slight.
B.
To understand how ocean acoustic tomography works, it is necessary to know how sound travels in the ocean.
C.
Ships are another possibility, but they would need to stop every 50 kilometers to lower measuring instruments.
D.
These variations amount to only about 2 to 3 percent of the average speed of sound in water, which is about i 500 meters per second.
【单选题】Which of the following, if presented as the first sentence of a succeeding paragraph, would most logically continue the discussion presented in the passage?
A.
The influence of volcanic eruptions on global weather patterns is almost completely understood at present.
B.
Scientists have only begun to understand, however, the effects of these wavelengths of light on the global environment.
C.
The majority of global cooling effects have thus been attributed to volcanic explosions.
D.
The human warming activities ameliorate by volcanic eruptions include those produced both by heavy industry and agriculture.
E.
The reason that sulfate aerosols take an unusually large time to disperse owes primarily to meteorological factors, including the jet stream.