【单选题】Most athletes have reached their peak by the time they are 20.
【单选题】To those disabled athletes, the most important thing is _______ win a gold, ______take part.
【单选题】He will spend six hours at his desk _______ he finishes his composition.
【单选题】She is going for vacation when she finishes ____________ her new book.
【简答题】详细叙述表面活性剂的作用有哪些?以及HLB值对乳化作用有何影响?
【单选题】建设项目是指需要一定量的投资,经过决策和实施(设计、施工等)的一系列程序,在一定的约束条件下形成()为明确目标的一次性事业。