阅读短文，回答问题。China is a big country. There is a population of 1.3 billion（13亿人口）in China. People speak Chinese in China. Beijing is the capital ofChina. It`s an old and famous city. It`s in the north .In China, there are manybig cities. Shanghai is a famous city, too. It`s in the east of China. I livein shanghai. My favourite city is Sanya. Sanya is in the south. Lhasa(拉萨)is in the west.

阅读下面短文，用括号内所给动词的适当形式填空 (必要时可加情态动词或助动词)。
    Many of us Chinese are Yao Ming's fans. Of course we all know he____( retire ) for several months . Yao made farewell(告别) conference Wednesday. He said he  ____(force )to make this decision by a series of foot and leg injuries. Yao played eight seasons in the NBA.
“Today is an important day for me and ____ (hold) a special meaning for both my basketball career and my future,”Yao said. “ I____(think) about my future for a long time. Today I am announcing a personal decision, ____ (end ) my career as a basketball player and officially retire. But one door is closing and another one____ (open).’’
    Yao said he____ ( return) to work with his former Chinese team, the Shanghai Sharks, with the possibility of____  (become) general manager. He already ____ (own) the club and wants to contribute more. He thanked a lot of people — his family, former coaches, even players like Shaquille O’Neal — “for making me a better player."
    Rockets(火箭队) general manager Daryl Morey was among those attending the farewell conference Wednesday. “I would be sorry if I wasn't here."“It's a big moment," Morey added. “Yao had a sense of humor, a great attitude and sense of responsibility. I hope we ____(continue) his culture in the NBA."

圆C的圆心在y轴正半轴上，且与x轴相切，被双曲线$x^2-\frac{y^2}{3}=1$的渐近线截得的弦长为$\sqrt{3}$，则圆C的方程为（     ）

在“用滑动变阻器改变电路电流”试验中，连接电路时，电键应处于____ 状态；在图（a）所示电路中，闭合电键前，滑片应移到变阻器的____ 端（选填“左”或“右”），试接触后发现电流表的表盘如图（b）所示，发生这一现象的原因是____ 。经思考后，重新连接进行实验，闭合电键后，电流表的示数如图（b）所示，此时电路中电流为____ 安。