题目

Every year, I circle the first day of spring on our calendar. In this way, it won't slip by_______. I'm not sure why _________ the calendar to announce spring's arrival, since it has so little bearing on the matter. Spring comes when it's good and ready; sometimes well before its _________day, sometime well after.For years, spring in our town was _________ by Leon and Jo Martin, who owned the Dairy Queen. Every year, they would _________ the words “Now Hiring” on their sign. I would walk past to see Leon and Jo Martin _________ for their spring opening. It was as _________ an indication of将萝卜磨碎制得提取液，取少量分别加到几支盛有pH为3～9的等量过氧化氢溶液的试管中，保持30℃温度，结果每一个试管都产生气体，重复上述实验，只是提取液的添加量减半。再次实验过氧化氢含量变化曲线如下图所示，请问： （1）萝卜提取液中含有的物质是________。 （2）为什么曲线A和B中，过氧化氢的含量的最低点位于同一直线上？________。 （3）A是第________次实验结果。理由是________。 （4）如果把提取液进行加热处理温度足够高，处理后进行第三次实验，结果是________。 这说明________。