A:he had a potential to live
B:he made good adjustment
C:his parents and teachers helped him a lot
D:he could fight to live with his blindness
请根据以上信息解答下列问题:
最近印尼的默拉皮火山发生了火山喷发,火山灰里含有大量的硅酸钙(CaSiO3),硅酸钙中硅元素的化合价为( )