水表要定时吹扫每班（）次，以保证其准确反映水位。

“乐天知命”是我们常听到的一句话，长久以来更是道家、儒家、佛教或禅宗所推崇的人生观。“乐天知命”的概念，最早可追溯自《易经·系辞上传》第四章。文中提到“与天地相似，故不违。知周乎万物，而道济天下，故不过。旁行而不流，乐天知命，故不忧。安土敦乎仁，故能爱。”翻译成白话，就是指一个人若能直道而行、不偏颇，就可以泰然处世；若能认识命运，就可以没有忧虑。
这段文字意在说明( )。

A．“乐天知命”是中国传统文化所推崇的人生观
B．“乐天知命”概念的来源
C．“乐天知命”的《易经》解释
D．“乐天知命”不是一件容易的事

蒸汽加热炉升温时，对称点火嘴可以加快升温速度。

调频无线电广播的频率范围是3×1O⁷～3×1O⁸Hz，则它的波长范围是______m．

We had guests last night who have not stayed in a B&B hotel ago. They did not want breakfast because that they were going out early in the morning. They came back lately and had some tea. I came into the living room and saw one of them just go through the kitchen door but turn on the light. He was looking for a glass the cupboard. He had no ideas that the kitchen was not for guests. I just smiled to me and thought, "What can I do We are guests after all. \

______

简述样品的缩分采用圆锥四分法的步骤？