$7:9=\frac{1}{7}:\frac{1}{9}$

小明学习了电路知识后，想利用发光二极管设计一个开关有指示灯的照明电路，晚间关闭照明灯后，利用二极管发出的光指示开关所在的位置。他共设计了4个电路，如图所示，其中L为白炽灯，规格为“220 V 60 W”、D为发光二极管，规格为“1.2 V 0.002 A”、S为单刀双掷开关、R为限流电阻。图中能够满足要求的电路是(  )

已知函数$f\left(x\right)=\left|lgx\right|$，$a>b>0$，$f\left(a\right)=f\left(b\right)$，则$\frac{a^2+b^2}{a-b}$的最小值等于（  ）.

    It was Mother's Day and I was shopping at the local supermarket with my five-year-old son,Tenyson.As we were1,we realized that only minutes earlier an2woman had fallen over at the entrance and hit her head on the ground3was with her, but there was blood everywhere and the woman was embarrassed and clearly in shock4,a lot of people stopped to help out.5we were walking towards the scene, Tenyson became very6about what had happened to the elderly couple. He7to me,“Mom, it's not much fun falling over in front of8”Seeing that there was a flower stall(摊位)at the front of the supermarket, he added, “Why shouldn't we9the lady a flower? It will make her feel better.”I was10that he'd come up with this11idea. So we went over and told the flower seller12we wanted.“Just take it,”she replied.“I13take your money for such a wonderful14”

    By now medical staff had arrived, and were15the injured woman. We gave the flower to the woman's husband and I told him it was16my son. At that, the old man started crying and said,“Thank you very much.”He then turned to me,“You have a17son. Happy Mother's Day to you.”

    The man bent down and gave his wife the flower, telling her who it was from18being badly hurt,the old lady looked up at Tenyson with19in her eyes and gave him a little20