新
以下为新SAT OG Test04 数学 Section4 Q20真题，考察大家对于代数和函数相关知识的掌握，这类知识点是每次考察重点，也经常会出难题。考生把这部分知识融汇贯通，明确知识点之间的内在关系，是获得高分的保证。
20
The mass of living organisms in a lake is defined to be the biomass of the lake. If the biomass in a lake doubles each year, which of the following graphs could model the biomass in the lake as a function of time? (Note: In each graph below, O represents (0, 0) .)
A . A
B . B
C . C
D . D
正确答案C
答案解析
Choice С is correct.
Since the biomass of the lake doubles each year, the bio- mass starts at a positive value and then increases exponentially over time. Of the graphs shown, only the graph in choice С is of an increasing exponential function.
Choice A is incorrect because the biomass of the lake must start at a positive value, not zero. Furthermore, this graph shows linear growth, not exponential growth. Choice В is incorrect because the biomass of the lake must start at a positive value, not zero. Furthermore, this graph has vertical segments and is not a function. Choice D is incorrect because the biomass of the lake does not remain the same over time.
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