题目

阅读下面短文，掌握其大意，从每题所给的A、B、C、D四个选项中，选出最佳选项。A Good Heart to Lean (倚靠) On More than I realized, Dad has helped me keepmy balance. When I was young, I didn't want to be seenwith my father. He was short and crippled (瘸), and when we 1 together, his hand on my arm for balance,people would look at us. It was 2 to coordinate (协调) our steps, and we didn't 3 much as we went along, just keeping silent 4 as we started out, he always said, Youset the pace (步伐). I will try to stay withyou. In my memory, my fatherwent to work ev在实验室里，某同学看到氢氧化钠试剂瓶的瓶口有白色粉末，如图所示．他对白色粉末的成分作出了一些猜测． 猜测一：可能是氢氧化钠猜测二：可能是碳酸钠猜测三：可能是氢氧化钠和碳酸钠为探究白色粉末的成分，他将该粉末溶于水，得到无色溶液，再迸行了如下实验： （1）根据实验现象推测，无色气体是___________．（2）在溶液2中滴加过量氯化钡溶液的目的是____________.　（3）由实验现象可知，猜测__________是正确的．