2013年12月14日，“嫦娥三号”携带“玉兔”成功登月。“玉兔”月球车在无大气的月面上行走时，可能遇到的考验是（   ）

计算：已知log₇3=a，log₇4=b，求log₇48．（其值用a，b表示）

    I like taking photos very much. Once I travelled by ship ____ a cloudy morning. It was in the afternoon____the weather turned fine. Therefore, I wanted to take some ____(photo). I was looking around and I saw next to me a lovely little girl sitting on her father's shoulders.____was lucky for me ____(meet) such a perfect moment—the girl was smiling and the surrounding view was beautiful. Without ____（think）, I took a picture of____little girl at that moment.

    Her mother was____(surprise) that a stranger was photographing her daughter. I explained that I was moved by that sight and showed them the photo on my digital(数字的) camera. They loved it very much. I said I could email it to them when I got home.____ (Final), they gave me their email address. The next day, I ____(send) them their daughter's photo as I had promised.

下列选项中的诗句填入《夏日西斋书事》一诗横线处，恰当的一项是(　　)
榴花映叶未全开，槐影沉沉雨势来。___________ ，满庭鸟迹印苍苔。