A:in it
B:i
C:in that
D:in which
Don't do any other things while you are doing your homework. So please _________ your MP3.
把下面的字的读音补充完整。
劈木柴
劈p____
等差数列{an}的前n项和记为Sn,若a2+a6+a10=3,则下列各和数中可确定值的是( )