For as long as humans have lived on the earth, they have made use of various forms of communication. Generally, this expression of thoughts and feelings has been in the form of oral speech. When there
Hello! My name is Joy. I’m a girl. I’m eleven. I’m in Class Eight, Grade Seven. This is my friend, Joan. She is twelve. She is in a high school. She is in Class Seven, Grade Eight. My English
让太阳光垂直照射到“△” 形孔上，那么地面上形成的光斑是：（ ）