题目

. Do dogs understand us? Be careful what you say around your dog. It might understand more than you think. A border collie named Rico recognizes the names of about 200 objects, say researchers in Germany. The dog also appears to be able to learn new words as easily as a 3-year-old child. Its word-learning skills are as good as those of a parrot or chimpanzee(黑猩猩).   In one experiment, the researchers took all 200 items that Rico is supposed to know and divided the into 20groups of 10 objects. Then the owner told the dog to go and fetch one of the items and bring it back. In four tests,R若溶液中由水电离产生的c(OH-)=1×10-14 mol·L-1，满足此条件的溶液中一定可以大量共存的离子组是(    ) A.Al3+、Na+、、Cl-                          B.K+、Na+、Cl-、C.K+、Na+、Cl-、                           D.K+、、、