(C)
Can dogs and cats live in perfect harmony in the same home People who are thinking about adopting a dog as a friend for their cats are worried that they will fight. A recent research has found a new recipe of success. According to the study, if the cat is adopted before the dog, and if they are introduced when still young (less than 6 months for cats, a year for dogs), it is highly probable that the two pets will get along swimmingly. Two-thirds of the homes interviewed reported a positive relationship between their cat and dog.
However, it wasn’t all sweetness and light. There was a reported coldness between the cat and dog in 25% of the homes, while aggression and fighting were observed in 10% of the homes. One reason for this is probably that some of their body signals are just opposite. For example, when a cat turns its head away it signals aggression, while a dog doing the same signals submission.
In homes with cats and dogs living peacefully, researchers observed a surprising behavior. They are learning how to talk each other’s language. It is a surprise that cats can learn how to talk "Dog", and dogs can learn how to talk "Cat".
What’s interesting is that both cats and dogs have appeared to develop their intelligence. They can learn how to read each other’s body signals, suggesting that the two may have more in common than we previously suspected. Once familiar with each other’s presence and body language, cats and dogs can play together, greet each other nose to nose, and enjoy sleeping together on the sofa. They can easily share the same water bowl and in some cases groom (梳理) each other.
The significance of the research on cats and dogs may go beyond pets—to people who don’t get along, including neighbors, colleagues at work, and even world superpowers. If cats and dogs can learn to get along, surely people have a good chance.
The underlined word swimmingly in Paragraph 1 is closest in meaning to（）
A. early
B. sweetly
C. quickly
D. smoothly