阅读下面这首诗，然后回答问题。

除夜野宿常州城外二首（其一）

苏轼

行歌野哭两堪悲，远火低星渐向微。病眼不眠非守岁，乡音无伴苦思归。

重衾脚冷知霜重，新沐头轻感发稀。多谢残灯不嫌客，孤舟一夜许相依。

【注】此诗作于宋神宗熙宁六年（1073）十一月，苏轼奉命前往常州等地赈济灾荒途中；除夜即除夕。

选出不同类别的单词（   ）

P是双曲线的右支上一点，M、N分别是圆（x＋5）²＋y²＝4和（x－5）²＋
y²＝1上的点，则|PM|－|PN|的最大值为                     （ ）             

A true friend is always helpful. I didn’t believe it 1 one thing happened to me when I was in Grade 7.
Li Jie was one of my classmates. He and I were also neighbours. He always listened to his mother 2 I didn’t like listening to my mother. I didn’t think it was necessary for 3 to teach me anything. Li Jie knew all about that but he said4 to me.
One weekend, Li Jie invited me to watch a film. I liked films very much so I went to the 5 with him happily. The film was about the love between a6 and her son. After watching it, I began to know how great the love of the mother was. I felt 7 that I didn’t listen to my mother before. I decided to think more about my mother than about8. After I told that to him, Li Jie smiled and said, “It’s really necessary for you to watch such a film. That was a good choice (选择) for both you and me.”
Suddenly, I knew9 he invited me to watch the film. Just at that time, I knew a true friend is always 10.

如图甲所示为一对间距为d且竖直固定放置的平行光滑金属导轨.在导轨下端接有一阻值为R的定值电阻，导轨上方放着一质量为m、长度为L的金属棒PQ(已知L>d).导轨下部处于垂直导轨平面向外的匀强磁场中，磁场上边界距导轨下端为h，磁感应强度随时间变化情况如图乙所示.金属棒PQ从t＝0以前某时刻自由释放，t₀时刻进入磁场并恰好开始做匀速直线运动，金属棒PQ与金属导轨的电阻不计，棒在下落过程中始终与导轨接触良好，求：