题目

在空格中填上适当的单词，使对话完整正确。一空一词 (含缩写词)。A: Look, there are so many milkweed plants (乳草植物) here. Did you plant them?B: No. They were planted by my son and it's he who takes care of them.A: Why did he want to plant such plants ? I mean, what made him start the work at the very beginning.B: It was seven years ago. Aiden's teacher taught them about monarch butterflies …A: Wait a minute. Monarch butterflies? What are they?B: Monarch butterflies are found in North America and occasionally on islands around thethe Caribbean. They are known 清晨父子两人同时从家出发，步行15千米到万泉公园中的海淀展览馆参与奥运会场馆建设投票．儿子比父亲每小时多走1千米，比父亲早到半小时，问二人每小时各走几千米？若设父亲每小时走x千米，则根据题意列出的方程是15x+1=15x-1215x+1=15x-12，父亲每小时走55千米．