—No, but I spend much time _____doing my homework.
A:on, in
B:in, on
C:in, in
下图为甲病(A、a)和乙病(B、b)的遗传系谱图,其中乙病为伴性遗传病,请回答下列问题:
已知等差数列an的公差为-3,若其前13项和S13=156,则a2+a5+a10=( )