题目内容：
阅读下列短文，回答题。Little Tom down the street calls our dog，“The keep dog”．Zip is a sheep dog．But when Tom tries to say“Sheep”．it xo mes out“keep”．And in a way Tom is right．Zip is always bringing things home for us to keep!I'll tell you about 80lne of them．
Zip’s first present was a shoe．It Was made of green silk．
We didn’t know how Zip found the shoe．But after a moment Mary，my big sister，told me the shoe had a strange smell．I nodded(点头)and held my nose．“What do you think it is?”
“It smells like something for cleaning．I think someone tried to clean a spot(污点)off the shoe．
Then he put it at the door to dry．”
“Along came Zip．And good-bye shoe!”I said．“We should take it back．”
“We can’t”，said my sister．
“Maybe little Tom is right．”Mary said．“Maybe Zip is a keep dog!”
The writer and Mary didn’t know__________. A．what Zip’s first present was
B．how Zip carried its first present home
C．who owned Zip’s first present
D．what Zip’s first present was made of
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