I remember that it was a fall morning when the orchestra teachers came into Miss Newell's third-grade classroom. “You have hands for the viola (中提琴),” Miss Ciano told me. I was excited because my hands were finally good for something. I told my parents I wanted to play, and naturally, they agreed.

    Since I first touched the viola, I haven't been able to put it down. Ignoring the difficulty, I am pulled closer to it each day.

    Classical music is truly my best friend. It is the trusted friend of every man, woman and child. Various feelings are expressed in classical music. I discovered that when I was eleven and played a Bach cello concerto (大提琴协奏曲) in a competition, the first movement was joyful, but the second movement was mysterious and full of pain. From that piece, I learned that music expressed not only feelings, but also sudden mood changes. By listening to classical music, I know that someone else share these feelings. Since I am lucky enough to be able to play classical music, I am comforted when I am upset. It gives me a way to escape from my problems for a short period. Classical music can express my joy, sadness and anger.

    Now look at that fall day and think how gullible I was for believing that anyone, even music teachers, could tell if hands were perfect for a certain instrument. I'm certain they told me I had “viola hands” not because they were fortune-teller, but because there was a lack of violists in our district. Classical music is one of the best things that ever happened to mankind. If you get introduced to it in the right way, it will become your friend for life.

    Both humans and animals have enemies. It is easy for us to know the difference between our friends and our enemies. But can other animals do the same? Elephants can! They can use their sense of vision and smell to tell the difference between people who pose a threat(威胁) and those who do not. In Kenya, researchers find that elephants react differently to clothing worn by men of the Maasai and Kamba ethnic groups. Young Maasai men spear(刺)animals and thus pose a threat to elephants; Kamba men are mainly farmers and are not a danger to elephants.

    In an experiment conducted by animal scientists, elephants were first presented with clean clothing or clothing that had been worn for five days by either a Maasai or a Kamba man. When the elephants noticed the smell of clothing worn by a Maasai man, they moved away from the smell faster and took longer to relax than when they noticed the smells of either clothing worn by Kamba men or clothing that had not been worn at all.

    Clothing color also plays a role. In the same study, when the elephants saw red clothing not worn before, they reacted angrily, as red is typically worn by Maasai men. Rather than running away as they did with the smell, the elephants acted aggressively(攻击地) toward the red clothing.

    The researchers believe that the elephants' emotional(情绪的) reactions are due to their different senses of the smells and the sights. Smelling a potential danger means that a threat is nearby and the best thing to do is run away and hide. Seeing a potential threat without its smell means that risk is low. Therefore, instead of showing fear and running away, the elephants express their anger and become aggressive.

圆、正方形、长方形、等腰梯形中有唯一条对称轴的是（   ）

我国已发现的鸟类有1166 ____种．