请教一道阅读题目

lionelfengUID: 2371460

请教一道阅读Because of its accuracy in outlining the Earth's subsurface, the seismic-reflection method remains the most important tool in the search for petroleum reserves. In field practice, a subsurface is mapped by line arranging a series of wave-train sources, such as small dynamite explosions, in a grid pattern. As each source is activated, it generates a wave train that moves downward at a speed determined uniquely by the rock's elastic characteristics. As rock interfaces are crossed, the elastic characteristics encountered generally change abruptly, which causes part of the energy to be reflected back to the surface, where it is recorded by seismic instruments. The seismic records must be processed to correct for positional differences between the source and the receiver, for unrelated wave trains, and for multiple reflections from the rock interfaces. Then the data acquired at each of the specific source locations are combined to generate a physical profile of the subsurface, which can eventually be used to select targets for drilling.
4. According to the passage, in the seismic-reflection
method which of the following have a significant
effect on the signal detected by the seismic
instruments
A presence of unrelated wave trains
B placement of the seismic instruments
C properties of rocks through which the wave
train has traveled
C选项在哪里体现出来了
谢谢

苏梳眠UID: 2717864

it generates a wave train that moves downward at a speed determined uniquely by the rock's elastic characteristics.
这句不是么，亲~

lionelfengUID: 2371460

2# 苏梳眠 谢谢斑竹~~