A:neither
B:either
C:none
D:both
S1= 1 + 2 + 3 =3
S2= 4 + 5 + 6 + 7 + 8 =10
S3= 9 + 10 + 11 + 12 + 13 + 14 + 15 =21,
…,
依此规律,那么S10=( )