计算3a﹣2a的结果等于____ ．

    Hi, my name is Li Tong. I'm from a big city. My parents are doctors in a hospital. I'm in Class 1. Mr Mu's class. He is a Chinese teacher. My favourite subject is history. I like reading history books in the library. On Saturday, I play basketball with my friend Su Qi. Fish is my favourite food.

Hello, I'm Su Qi. I'm from the farm near the city. My parents are farmers. I'm in Class 3. Miss Bi's class. She is a maths teacher. English is my favourite subject. I can see a lot of vegetables on the farm. So I like reading the books about vegetables. Noodles are my favourite food.

右图是某区域气温分布图，关于图中信息叙述正确的是：

下列是我国未成年人保护法规定的学校保护的内容有（    ）

①学校要全面贯彻国家的教育方针      ②学校尊重学生的人格尊严，不得对学生实施体罚

③网吧不得接纳未成年人上网              ④学校组织集体活动要有利于学生的健康成长