—Would you like ____ camping with me ?
—I’d like to . But I am busy ____ my homework.
从4个班级的学生中选出6名学生代表,若每一个班级中至少有一名代表,则选法总数为( )
“不登高山,不知天之高也;不临深溪,不知地之厚也。”相对于学习来说,这表明( )