A:常温下玻璃是导体
B:火焰将电路直接连通
C:玻璃加热到一定程度可以导电
D:导体和绝缘体不可能转化
— I tried to make Alice her mind but I found it difficult.
—Well, I saw you that when l went past.
设0<α<π2,a是大于0的常数,函数F(α)=1cosα+a1-cosα,若F(α)≥16恒成立,则a的取值范围是( )