题目

阅读下面短文，按照句子结构的语法性和上下文连贯的要求，在空格处填入一个适当的词或使用括号中词语的正确形式填空，并将答案填写在答题卡标号为16—25的相应位置上。 Although it could not compete with the speed of email today, the 1800’s experienced a revolution in communication that played an important role in creating the tradition of the Christmas greeting card. ____(help) by the new railway system, the public postal service made corresponding a popular past time. In England, Sir Henry Cole recognized the advantage of ___m下列各组溶液中，不需要使用别的试剂就可以区别开来的是（　　） A、K2SO4、BaCl2、NaNO3 、NaClB、HCl、NaOH、NaNO3 、Na2SO4C、Na2SO4、NaCO3、BaCl2、HClD、KCl、AgNO3、KNO3、HCl