题目

Did Mary visit that old town by ________ last week? A) her                   B) she                  C) hers                  D) herself 答案：D  化学电池是 ___                     的装置，其反应的基础是 _                    。写出铜锌原电池（稀硫酸为电解质）的电极反应：正极                      ，负极                           。