A:to have read to
B:to have been read to
C:having been read to
D:being read to
已知{an}为等差数列,a1+a3+a5=105,a2+a4+a6=99,以sn表示{an}的前项和,则使得sn达到最大值的是( )
V/cm3
10
20
30
40
50
60
F/N
7
6
5
4
3
2