Babies are not just passing idle time when they stare at the television--they are actually learning about the world, U. S. researchers said. Parents may want to limit what their babies see on television, based on the study, said Donna Mumme, assistant professor of psychology at Tuffs University in Boston, who led the research. "Children as young as 12 months are making decisions based on the emotional reactions of adults around them," Mumme said in a statement. "It turns out they can also use emotional information they pick up from television." Mumme's team already knew that babies watch other children and adults for information about the world. A mother urging her baby to eat some "yummy" soup or a brother crying in fear when a dog approaches can influence a baby's reaction. Mumme's team tested babies to determine if television has the same influence, showing actors reacting on a videotape to objects such as red letter holder, a blue ball, and a yellow lubber. Babies aged 10 months or 12 months were later given the same objects to play with. Ten-month-olds did not seem to be influenced by the videos, but the 1-year-olds were. When the actors acted naturally or positively to an object, the babies happily played with them. But if the actor had seemed afraid or disgusted, the babies would avoid the object. Mumme reached his conclusion by  _  .
measuring the time babies spent in front of TV making TV programs and advertisements for kids showing actors how to react to blue balls observing small babies' reactions to TV programs
Question: Babies are not just passing idle time when they stare at the television--they are actually learning about the world, U. S. researchers said. Parents may want to limit what their babies see on television, based on the study, said Donna Mumme, assistant professor of psychology at Tuffs University in Boston, who led the research. "Children as young as 12 months are making decisions based on the emotional reactions of adults around them," Mumme said in a statement. "It turns out they can also use emotional information they pick up from television." Mumme's team already knew that babies watch other children and adults for information about the world. A mother urging her baby to eat some "yummy" soup or a brother crying in fear when a dog approaches can influence a baby's reaction. Mumme's team tested babies to determine if television has the same influence, showing actors reacting on a videotape to objects such as red letter holder, a blue ball, and a yellow lubber. Babies aged 10 months or 12 months were later given the same objects to play with. Ten-month-olds did not seem to be influenced by the videos, but the 1-year-olds were. When the actors acted naturally or positively to an object, the babies happily played with them. But if the actor had seemed afraid or disgusted, the babies would avoid the object. Mumme reached his conclusion by  _  .
A. measuring the time babies spent in front of TV
B. making TV programs and advertisements for kids
C. showing actors how to react to blue balls
D. observing small babies' reactions to TV programs
Answer: