题目

完形填空 Every year on my birthday, from the time I turned twelve, a bunch of white gardenia (栀子花) was delivered to my house. No card or note came with it.1to the flower shops were not helpful at all—it was a cash2.After a while I stopped trying to 3who the sender was and just delighted in the beauty and perfume of the white flowers in soft pink paper. But I never4 imagining who the sender might be. Some of my 5moments were spent daydreaming about it. My mother6to these imaginings. She would ask me whether there was someone for whom I had done a(n)7kindness and said that he/ she mi已知：①A、B、C、D四种物质均含元素X，有的还可能含有元素Y、Z。元素Y、X、Z的原子序数依次递增。 ②X在A、B、C、D中都不呈现它的最高化合价。 ③室温下单质A与某种常见一元强碱溶液反应，可得到B和C。 ④化合物D受热催化分解，可制得元素Y的单质。（1）元素X是 _________，Z是_____________ 。（2）写出③中反应的化学方程式：____________________ 。（3）写出④中反应的化学方程式：_____________________。