A. They can make people feel happy.
B. They can make people strong and healthy.
如图,▱ABCD中,对角线AC,BD交于点O,点E是BC的中点.若OE=3cm,则AB的长为( )
将质量相等的铝粉和铁粉分别与质量、浓度均相同的稀硫酸充分反应,下列所述的反应情况与图示可能相符的是()