问题
单项选择题
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．33
答案
参考答案：C
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a1，公差d=2，共有10项，其和Sn=100，由等差数列的求和公式可得：
[*]
所以a8=1+7×2=15