点通过矩阵M₁=$\left(\begin{array}{cc}1& 0\\ 0& \frac{1}{2}\end{array}\right)$和M₂=$\left(\begin{array}{cc}1& 0\\ 0& \frac{1}{3}\end{array}\right)$的变换效果相当于另一变换是（　　）

选用方框中的句子完成对话，其中有两项是多余的。
Li Lei: Excuse me. ____
Mr. Smith: Yes. And you are.. . ?
Li Lei: I’m Li Lei. Your friend Miss Wu is busy at the moment. She asks me to meet you. Welcome to Hangzhou, Mr. Smith.
Mr. Smith: Thank you.
Li Lei: By the way____ 
Mr. Smith: No. This is my second time. I came here in 1998 for the first time.
Li Lei:____
Mr. Smith: I like it very much. It’s very beautiful and famous in the world. And the people here are quite friendly.____
Li Lei: I’m glad you like the city. And now Hangzhou is becoming more and more beautiful.____
Mr. Smith: I think so. Thank you very much for meeting me.
Li Lei: It’s a pleasure.

2014年3月14日，“玉兔号”月球车成功在距地球约384400公里远的月球上自主唤醒，将384400保留2个有效数字表示为（　　）

如图为五个椭圆交叉构成的图案，椭圆内分别写了C₂H₅OH、CO₂、Fe₂O₃、FeCl₃和NaOH五种物质，图中相连的两种物质均可归为一类，相交的部分A、B、C、D为其相应的分类标准代号．请回答下列问题：