等腰三角形的两边长分别为6和11，则它的周长为（　　）

有两只外形相同、灯丝长度相等的灯泡L₁和L₂，在它们的铭牌上只能看清“220V”字样，而看不清它们额定功率的大小．甲、乙、丙三位同学对它们进行了探究：甲同学发现L₁的灯丝粗一些，认为L₁的电阻小，所以L₁的额定功率比L₂小；乙同学把两灯串联在同一电路中，发现L₂比L₁亮，认为L₂的额定功率大；丙同学把两灯并联在同一电路中，发现L₁比L₂亮，认为L₁的额定功率大．你认为哪位同学的探究是正确的（　　）

阅读短文，根据要求完成下面各小题。

  A road is just like a bridge between two places. The Silk Road has been a bridge between East and West. But the Silk Road is not a single route! It is a series of trade and cultural transmission routes. From the time Zhang Qian opened up the world-famous Silk Road during the Han Dynasty, until the Yuan Dynasty, it enjoyed a history of about 1,600 years.

 This ancient road begins at Chang'an (now Xi'an), and it reaches Dunhuang, where it divides into three, the Southern Route, Central Route and Northern Route. And then it ends in Eastern Europe, near the Mediterranean Sea(地中海). The Silk Road is about 6,500 kilometers long. It goes across one-fourth of the planet. (3)In fact, there is another trade road which is called the “Silk Road on the Sea” in the southwest of China.

 The Silk Road was very important to both China and the rest of the world. Besides trade, knowledge about science, arts and technologies were shared across the Silk Road. The Four Great Inventions of China was introduced to the West and Chinese also knew about the religions of the West. (4)In this way, languages and cultures developed and influenced each other. Today, places along the Silk Road are great places of interest, such as the Terracotta Warriors in Xi'an and Mogao Grottoes in Dunhuang, Gansu.