I used to be a very self-centered person, but in the past two years I have really changed. I have started to think about other people 1 I think about myself. I am happy that I am becoming a 2 person.

    I think my change started when I was at Palomar College. At first, I just wanted to get my 3 and be left alone. I thought I was smarter than everyone else, so I hardly ever 4 to anyone in my classes. By the end of my first semester, I was really 5. It seemed as if everyone but me had made friends and was having fun. So I tried an experiment. I started asking people around me how they were doing, and if they were having trouble, I offered to help. That was really a big 6 for me. By the end of the year, I had several new friends, and two of them are still my best friends today. 

    A bigger cause of my new 7, however, came when I took a part-time job at a Vista Nursing Home. One old lady there who had Alzheimer's disease(老年痴呆症) became my 8. Every time I came into her room, she was so 9 because she thought I was her daughter. Her real daughter never 10her, so I took her place. She let me 11 that making others feel good made me feel good, too. When she died, I was heartbroken, but I was very grateful to her.

    I think I am a much 12 person today than I used to be, and I hope I will not 13 these experiences. They have 14 me to care about other people more than about myself. I 15 who I am today, but I could not say that a few years ago.

生物实验中使用的琼脂来源于某些藻类植物。（判断对错）

重要的历史文献如同时代的缩影，见证了一段不平凡的历史。请正确填写文献名称。
（1）“凡未经国会准许，借口国王特权，为国王而征收……皆为非法”——____ 
（2）“为人占有而做奴隶的人们都应在那时（1863年元旦）及以后永远获得自由”——____ 
（3）“在权利方面，人们生来是而且始终的自由平等的”——____ 

已知 $\overrightarrow{OA}=\left(1,1,0\right)$ ， $\overrightarrow{OB}=\left(4,1,0\right)$ ， $\overrightarrow{OC}=\left(4,5,-1\right)$ ，则向量 $\overrightarrow{AB}$ 和 $\overrightarrow{AC}$ 的夹角的余弦值为（   ）