短文改错（本题有10小题，每小题1分，共10分）

Dear Mum and Dad,

I expect you are surprised at hearing from me so soon.

The fact is I can’t come home this Saturday                           76.          

as I plan. I have had an accident and hurt my                           77.          

back, and it is not serious. What happened was                         78.          

this. I was riding in the street with Mike when                          79.         

I felt down and lay on my back. I thought it a                          .80         

great joke at the first. But when I tried to stand up,                   81.         

I felt a pain on my back and could hardly move.                       82.         

Don’t worry about me. Mike and his family is               83.         

so kind to me. I will better soon and there is no need                   85.         

for you to come there. I will write to you again soon.                 85.        

下列是明朝诗人于谦的《石灰吟》：①千锤万凿出深山，②烈火焚烧若等闲，③粉身碎骨浑不怕，④要留清白在人间．

（1）诗中隐含物理变化的诗句是______．（填序号）

（2）请写出诗中所涉及的化学方程式______．