How fit are your teeth? Are you lazy about brushing them? Never fear: An inventor is on the case. An electric toothbrush senses   how long and how well you brush, and it lets you track  your performance on your phone. The Kolibree toothbrush was exhibited at the International Consumer Electronics Show in Las Vegas this week. It senses how it is moved and can send the information to an Android phone or iPhone via a Bluetooth wireless   connection. The toothbrush will be able to teach you to brush right (don't forget the insides of the teeth!) and make sure you're brushing long enough. "It's kind of like having a dentist actually watch your brushing on a day-to-day basis," says Thomas Serval, the French inventor. The toothbrush will also be able to talk to other applications  on your phone, so developers could, for example, create a game controlled by your toothbrush. You could score points for beating monsters among your teeth. "We try to make it smart and fun," Serval says. Serval says he was inspired by his experience as a father. He would come home from work and ask his kids if they had brushed their teeth. They said "yes," but Serval would find their toothbrush heads dry. He decided he needed a brush that really told him how well his children brushed. The company says the Kolibree will go on sale this summer, from $99 to $199, and the U.S. is the first target market. ( ) What can we infer about Serval's children?
They were unwilling to brush their teeth They often failed to clean their toothbrushes. They preferred to use a toothbrush with a dry head. They liked brushing their teeth after Serval came home.
Question: How fit are your teeth? Are you lazy about brushing them? Never fear: An inventor is on the case. An electric toothbrush senses   how long and how well you brush, and it lets you track  your performance on your phone. The Kolibree toothbrush was exhibited at the International Consumer Electronics Show in Las Vegas this week. It senses how it is moved and can send the information to an Android phone or iPhone via a Bluetooth wireless   connection. The toothbrush will be able to teach you to brush right (don't forget the insides of the teeth!) and make sure you're brushing long enough. "It's kind of like having a dentist actually watch your brushing on a day-to-day basis," says Thomas Serval, the French inventor. The toothbrush will also be able to talk to other applications  on your phone, so developers could, for example, create a game controlled by your toothbrush. You could score points for beating monsters among your teeth. "We try to make it smart and fun," Serval says. Serval says he was inspired by his experience as a father. He would come home from work and ask his kids if they had brushed their teeth. They said "yes," but Serval would find their toothbrush heads dry. He decided he needed a brush that really told him how well his children brushed. The company says the Kolibree will go on sale this summer, from $99 to $199, and the U.S. is the first target market. ( ) What can we infer about Serval's children?
A. They were unwilling to brush their teeth
B. They often failed to clean their toothbrushes.
C. They preferred to use a toothbrush with a dry head.
D. They liked brushing their teeth after Serval came home.
Answer: