小夏在研究口琴的发声原理时，拆掉了口琴外壳，发现在气孔边分布着长短、厚薄都不同的一排铜片（如图所示）．吹口琴时，在气流的冲击下，铜片____发出声音．对不同气孔吹气，改变了声音的____；在同一气孔处用不同的力度吹气，改变了声音的____．

《手拉手》歌词的末句“推倒一切障碍，让那理解的歌声永远飞扬”有怎样的深刻含义？

正比例函数y=2x和反比例函数$y=\frac{2}{x}$的一个交点为(1，2)，则另一个交点为（ ）

        These days, many students like playing 3D games. Do you know what 3D games are like? In most 3D games, game players need to control (控制) a character. The character can be a robot or a soldier (士兵). Game players usually use the mouse to make the character move around in his own world. Game players can find things such as food and weapons (武器) to help them go on with the game. The character can go straight, sit down, turn left, turn right or pick up things in the game.
        Some 3D games have many levels (等级). The character needs to finish different goals for each level. Game players can play against their computers, and sometimes they can play with other players online. It’s great fun to play 3D games. But playing 3D games for long is not good for our study.

假如要造一座四面窗户都朝南的房屋，那么这座房屋应建在（  ）