新能源的开发和利用是能源研究的主要课题，太阳能电池是将太阳能转化为____ 能；核电站是利用____ 能来发电的．

量一量，想一想。

    长方形的长是____厘米，宽是____厘米，从中截取一个最大的正方形．正方形的边长是____厘米．

Mrs. Green is________ mother. They are________.

Dear Sally,

    Thank you for your e-mail and the photo of New York. Here are some photos of my family trip in Wuhan. In the first photo, my sister Jane is wearing Chinese traditional clothes on the Yellow Grower. In the second picture, my father and I are swimming in a river. It's so cool! In the next picture, my parents, Jane and I are eating great noodles. Its name is hot dry noodles. It looks very nice!

    In the last picture, my family people are at my friend's home. We are having some mooncakes because it's the Mid-autumn Festival. It's an important festival in China. On this day, all the families get together and have a happy dinner.

    I think Wuhan is a nice city in China. The people there are friendly. One day I wish to go there again.

Yours,

David

世界上领土面积第二是加拿大；第三是中国，最小的是____。