A:平均增加2个单位
B:平均增加1.5个单位
C:平均减少2个单位
D:平均减少1.5个单位
The Red Army soldiers had to fight ________ all kinds of difficulties in their fight ________ the people's freedom.
Research shows that people feel unhappy and worried when they have nothing to do.________,the happiest are those who are busy.
某校举行地震逃生演练活动。小明同学对此不以为然:又没发生地震,用得着那样练吗?他的这种想法是( )