单选题
On a certain 10-question test, each question after the first question is worth 2 points more than the previous question. If the greatest number of points that can be scored on the test is 100, how many points is the eighth question worth?
A、
9
B、
14
C、
15
D、
19
E、
(E) 33
【正确答案】
C
【答案解析】
[解析] 根据题意可知，这10个问题的分数构成了一个等差数列，设其首项为a
1
，公差d=2，共有10项，其和S
n
=100，由等差数列的求和公式可得：
[*]
所以a
8
=1+7×2=15
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