I used to be an active girl. But two years ago, an English speech contest held in my school changed me a lot. 1 I was so nervous that I couldn't remember anything. Not long after I began my speech, the hall turned noisy. It seemed that all the students were laughing at me. I knew I failed. 2 I didn't want to express my ideas in public, even in class. One day, my science teacher asked us why the trees in forests were much taller than those in other places. 3 " Because there's not enough space in forests for the trees to expand (伸展) their branches. Of course they have to grow taller than the others, " I said in a low voice. 4 Hearing this, my face turned red at once. Then the teacher explained the trees in forests had to grow taller to receive more sunlight. "If not, they would die. Living in groups makes them grow taller," he said. 5 I raised my head slowly and found the teacher was looking at me. His eyes seemed as warm as the sunshine. I realized that I should be brave and change myself.