A:how we can be on time
B:what we are going to do
C:why we get to school late
D:if we will arrive at the meeting on time
carry(过去式)____
已知等差数列{an}的前n项和为Sn,且S2=10,S5=55,则过点P(n,an)(n∈N*)和Q(n+2,an+2)(n∈N*)的直线的一个方向向量坐标可以是( )