The idea for a science experiment can come from an unusual place. After watching a YouTube video of a dancing bird named Snowball, a scientist in California decided to study the ability of animals to keep the beat.
Bird lovers have long claimed that their pets have rhythm, and there are many videos of dancing birds online. Until now, scientists have suspected that humans are the only animals that can accurately keep rhythm with music.
Thanks to Snowball, that scientific opinion is changing. Snowball is a cockatoo, a kind of parrot, and his favorite song is "Everybody" by the Backstreet Boys. When he hears the song, he moves his feet and rocks his body with the tempo, or pace of the music, as though he is the only bird member of the boy band.
Aniruddh Patel is a neuroscientist, or a scientist who studies how the brain and the nervous system contribute to learning, seeing and other mental abilities. He works at the Neurosciences Institute in San Diego. After seeing Snowball's dance online, Patel visited the cockatoo at the bird rescue facility he's called home for two years. The scientist played "Everybody" for Snowball and also played versions of the song that were sped up or slowed down. Sometimes, Snowball danced too fast or too slowly. Often, when there was a change in tempo, Snowball adjusted his dancing to match the rhythm. In other experiments, scientists have observed the same abilities in preschool children.
Patel isn't the only scientist who has studied Snowball's moves. Adena Schachner, who studies psychology at Harvard University, also wanted to know more about the dancing bird. Schachner's team played different musical pieces for Snowball and a parrot named Alex, as well as eight human volunteers. The scientists observed that the birds and thehumans kept time to the music with about the same accuracy.
Schachner and her team watched thousands of YouTube videos of different animals moving to music. Not all the animals could dance, however. From watching the videos, the scientists observed that only animals that imitate sounds, including 14 parrot species and Asian elephants, accurately moved in time to music.
The underlined words "that scientific opinion" in the third paragraph refer to the theory that __________.

A．birds like Snowball have the ability to keep the beat

B．humans are the only animals that can accurately keep rhythm with music

C．the brain and the nervous system contribute to some mental abilities

D．bird pets can have their special rhythm under human's instruction

From the fourth paragraph we may know that __________.

A．Patel is the only scientist who has studied Snowball's moves

B．Snowball is able to adjust his dancing to match the rhythm

C．Snowball cannot dance to the versions of the song "Everybody"

D．it is the brain and the nervous system that control the mental abilities

The idea of studying animals' ability to keep the beat comes from __________.

A．bird lovers' discovery

B．humans' musical sense

C．the same abilities in children

D．videos of dancing birds