已知等差数列{an}中,a2=6,a5=15,若bn=a2n,则数列{bn}的前5项和等于[ ]
A.30
B.45
C.90
D.186
答案:C
Helen got up too late this morning, so she went to school _____ breakfast.
A.without
B.through
C.for
D.with
钢包精炼炉内吹氩效果主要有哪些?