Which of the following is NOT the goal of Earth Day 2000？
A. Clean air.
B. Clean water.
Clean automobiles.
D. Clean investment.
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控制加热蒸汽流量和控制冷凝液排出量的加热器控制方案的特点各是什么？
分程控制系统与简单控制系统、连续型选择性控制系统的主要区别是什么？分别画出分程控制系统与连续型选择性控
"... generation gap is narrowing. "means__________. 查看材料
A. the adolescents now become timid
B. parents come to get along with their children
C. the vast majority of teenagers share most of their parents" values and ideas
D. parents and teenager don" t like to quarrel
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