铝合金吊顶上风口、检修口、灯罩等预留洞，均需增设主龙角，并且吊扇的吊钩不应设置在龙骨上。( )
参考答案：对
Mozart started writing music ______________ he was four years old.
A until B after C before D when
尖晶石的典型包裹体为八面体负晶.
