题目

He is         English boy. We all like him. A. a                          B. an                            C. the                           D. / 答案：B  本题考查冠词。English的读音以元音音素开头,所以用不定冠词an,an English boy意为“一个英国男孩”。已知数列{an}满足2an+1=an+an+2 (n∈N*),它的前n项和为Sn，且a3=10,S6=72.若bn=an-30,求数列{bn}的前n项和的最小值.