For those who study the development of intelligence（智力）in the animal world, self-awareness is an important measurement. An animal that is aware（意识）of itself has a high
level of intelligence.
Awareness can be tested by studying whether the animal recognizes itself in the mirror, that is, its own reflected image（反射出的影像）．Many animals fail this exercise bitterly, paying very little attention to the reflected image. Only humans, and some intelligent animals like apes and dolphins, have been shown to recognize that the image in the mirror is of themselves.
Now another animal has joined the club. In the Proceedings of the National Academy of Sciences, researchers report that an Asian elephant has passed the mirror self-reflection test. "We thought that elephants were the next important animal," said Diana Reiss of the Wildlife Conservation Society, an author of the study with Joshua M. Plotnik and Fans B．M. de Waal of Emory University. With their large brains, Reiss said, elephants "seemed like cousins to apes and
The researchers tested Happy, Maxine and Patty, three elephants at the Bronx Zoo. They put
an 8-foot-square mirror on a wall of the animals' play area (out of the sight of zoo visitors) and recorded what happened with cameras, including one built in the mirror.
The elephants used their long noses to find what was behind it, and to examine parts of their bodies.
Of the three, Happy then passed the test, in which a clear mark was painted on one side of her face. She could tell the mark was there by looking in the mirror, and she used the mirror to touch the mark with her long nose.
Diana Reiss said, "We knew elephants were intelligent, but now we can talk about their intelligence in a better way."
45. What can mirror tests tell us about animals?
A. Whether they have large brains.
B ．Whether they have self-awareness.
C. Whether they enjoy outdoor exercises.
D. Whether they enjoy playing with mirrors.
46. Why does the author mention apes and dolphins in the text?
A. They are most familiar to readers.
B ．They are big favorites with zoo visitors.
C. They are included in the study by Reiss.
D. They are already known to be intelligent.
47. What made Happy different from Maxine and Patty?
A. She used her nose to search behind the mirror.
B. She recognized her own image in the mirror.
C. She painted a mark on her own face.
D. She found the hidden camera.