语法填空（共10小题，每小题1.5分，满分15分）
阅读下面短文，按照句子结构的语法性和上下文连贯的要求，在空格处填入一个适当的词或使用括号中词语的正确形式填空。
In the 1960s, a family that owned a farm near Belfast, Tennessee kept a bull chained __31_____ an oak tree.  The bull paced around the tree, ____32_____(drag) the heavy iron chain, which led to a groove (槽) in the bark (树皮). ____33_____groove was deepened over the years. Though for whatever reason, it did not kill the tree.
34  some years, the family took their bull away. They cut the chain, leaving the loop around the tree and one link 35  (hang down).
Then one year, agricultural catastrophe struck Tennessee in the form of Dutch oak disease. All of the oaks lining the road leading to the farm became infected    36   died. Everyone thought that the old oak tree would be the next. The farm owners considered  37   (go) the safe thing: pulling it out and chopping it up into firewood before it died.
38   (surprise), the tree did not die. Nobody could understand   39   it was the only oak still standing in the county. It' s said that   40   doesn' t kill you will make you stronger. Or, as a plant pathologists (病理学家 ) put it , "Life breaks us all, but afterwards, many of us are strongest at the broken places."