设{an}是由正数组成的等比数列，Sn是其前n项和．（1）证明lgSn+lgSn

Passage One

Concerning one’s sitting posture, which of the following is correct

A．One should prop his head with his elbows on the table.

B．One should hold an extra napkin.

C．One should be upright in his chair.

D．One should lean against the back of his chair.

“添加排除”对话框中如何配置
[*]

如何认识教师与学生在教育过程中的地位问题？ 

用相对直角坐标设置的点涉及到（）

A、上一指定点或位置

B、球坐标原点

C、屏幕左下角点

D、以上都是

在管环型燃烧室中，联燃管连通（）个火焰筒.

A.一

B.两

C.几

D.每