[填空题]What are dogs trained to do in Switzerland

[填空题]According to the passage, what were dogs trained for in the past Dogs were trained for _________ in the past.

[填空题]What are dogs used to do in Iceland and thus are considered very important there

[填空题]

What are people trained to do in order to avoid conflicts

[单项选择]What can dogs see The answer to this question is disappointing; dogs (67) see no colors. The answer is disappointing (68) many owners of dogs will naturally be sorry that their dogs cannot see colors which to them are beautiful. But then, they may (69) that clogs have an extraordinary (70) sense of smell. The dog’s world is (71) in enjoyable smells, (72) it may be colorless.
How do we know if dogs are color-blind This has been tested in the same way (73) it has been discovered what dogs can hear. The (74) has been made to train dogs to salivate (流口水) when they are shown (75) different colors. Such experiments have (76) failures; it has been found impossible to make dogs (77) colors from one another (78) signals for their dinner. This question requires further (79) with other techniques, but so far as the available scientific evidence A. rich
B. vast
C. scarce
D. obscure