13．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 200objects，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 200items that Rico is supposed to know and divided them into 20groups of 10objects．Then the owner told the dog to go and fetch one of the items and bring it back．In four tests，Rico got 37out of 40commands right．As the dog couldn't see anyone to get clues，the scientists believe Rico must understand the meanings of certain words．
In another experiment，the scientists took one toy that Rico had never seen before and put it in a room with seven toys whose names the dog already knew．The owner then told Rico to fetch the object，using a word the dog had never heard before．
The correct object was chosen in seven out of l0tests，suggesting that the dog had worked out the answer by process of elimination（排除法）．A month later，Rico remembered half of the new names，which is even more impressive．
Rico is thought to be smarter than the average dog．For one thing，Rico is a border collie，a breed （品種）known for its mental abilities．In addition，the 9-year-old dog has been trained to fetch toys by their names since the age of nine months．
It's hard to know if all dogs understand at least some of the words we say．Even if they do，they can't talk back．Still，it wouldn't hurt to sweet-talk your dog every now and then．You might just get a big，wet kiss in return!
72．From paragraph 2we know thatC．
A．a(chǎn)nimals are as clever as human beings
B．dogs are smarter than parrots and chimpanzees
C．chimpanzees have good word-learning skills
D．dogs have similar learning abilities as 3-year-old children
73．Both experiments show thatB．
A．Rico is smart enough to get all commands right
B．Rico can recognize different things including toys
C．Rico has developed the ability of learning mathematics
D．Rico won't forget the names of objects once recognizing them
74．Which of the following statements is true？B
A．The purpose of the experiments is to show the border collie's mental abilities．
B．Rico has a better memory partly because of its proper early training．
C．The border collie is world-famous for recognizing objects．
D．Rico is born to understand its owner's commands．
75．What does the writer want to tell us in the last paragraph？D
A．To train your dog．
B．To talk to your dog．
C．To be friendly to your dog．
D．To be careful with your dog．
