about 20 percent of.后接的谓语用单数还是复数?percent是可数名词吗

An estimated 80 percent of American adults think music lessons, though at times boring and challenging in the eyes of some kids, improve children’s ability to learn or their performance in school . They say that the satisfaction for learning to play a new song helps a child express creativity.
Researchers at Harvard University, however, have found that there’s one thing musical training does not do. Samuel Mehr, the leading researcher of the new study, said it is wrong to think that learning to play a musical instrument improves a child’s intellectual development. The evidence comes from studies that measured the mental ability of two groups of 4-year-olds and their parents. One group attended music class; the comparison group went to a class that places importance on the optical arts-arts that can be seen.
“We found no evidence for any advantage on any of these tests for the kids participating in these music classes,” said Mehr.
Samuel Mehr says researchers have carried out many studies in an effort to learn whether musical training can make children smarter. Only one study seems to show a small percentage increase in IQ, intellectual scores among students after one year of music lessons.
He does not believe that IQ is a good measure of a child’s intelligence. Therefore, the researchers in his study compared how well children in the musical training group did on mental processing tasks, then the results were compared to those of children who did not take lessons.
Music lessons may not offer children a fast easy way to gain entry to the best schools later of their life, but the training is still important.
Mr Mehr notes that the works of writer William Shakespeare are not taught , so the children will do better in physics. He says Shakespeare is taught because it is important for cultural reasons.“And I don’t think music needs to be any different than that.”
小题1:What attitude do most American grown-ups have towards music lessons? _________

A．Uninterested

B．Approving

C．Doubtful

D．Uncertain

小题2:The underlined word“optical”in Paragraph 2 probably means .

A．visual

B．colorful

C．traditional

D．serious

小题3:According to Samuel Mehr, _________ .

A．many studies show that music training can improve IQ

B．IQ is a good measure of a child’s intelligence

C．music can enable a child to go to a better school

D．music should be taught for cultural reasons

小题4:The study shows that .

A．early music training has negative effects

B．musical lessons should be stopped at school

C．musical training doesn’t improve kids’ intelligence

D．playing musical instrument makes kids more creative