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Mathematics>Standard Multiple Choice

Read the following SAT test question and then click on a button to select your answer.

During the process of radioactive decay, a "parent" material produces a new "daughter" material, which further decays into a stable material. During an experiment involving radioactive decay, the mass M, in micrograms, of daughter material changes over time t, measured in hours as shown in the graph above. What is the significance of the point shown on the graph?

A. The point shows the mass of the daughter material at the beginning of the experiment.
B. The point shows the mass of the daughter material when the mass was increasing at its fastest rate.
C. The point shows the amount of time the daughter material takes to decay into stable material.
D. The point shows the maximum mass of the daughter material and the number of hours since it was created that its mass reached this maximum.

答案和解析

答案：D

解析：

Choice D is correct. The point indicated is the highest point on the graph. Since t represents the time in hours since the daughter material was created and M represents the mass of the daughter material, the point shows the values of t and M when M is greatest. Therefore, the point shows the maximum mass of the produced substance and the number of hours since it was created that its mass reached this maximum.