【单选题】

Not long ago, many people believed that babies only wanted food and to be kept warm and dry. Some people thought babies were not able to learn things (67) they were five or six months olD、 (68) doctors in the United States say babies begin learning (69) their first day of life. Research scientists note that babies are (70) influenced by their environment.A、baby learns to get the best care (71) by smiling to please her mother or other caregiver. This is (72) babies learn to connect and communicate with other people.

TheAmerican researchers say this ability to learn exists in a baby (73) before birth. They say newborn babies can (74) and understand sounds they heard while they were still (75) inside their mothers.
Many experts say the first years of a child’s life are important for all (76) development.AnAmerican study shows how mothers can influence (77) development and language skills in their children.
The study (78) more than 1,200 mothers and children. Researchers studied the children from the age of one month to three years. They observed the mothers (79) with their children four times during this perioD、
The researchers attempted to (80) the sensitivity (敏感性) of the mothers. The women were considered sensitive if they (81) their children’s activities and did not interfere unnecessarily. They tested the children (82) thinking and language development when they were three years olD、
Experts say the first three years of a child’s life is the most (83) period of language and speech development. Language and communication skills (84) to develop best in an environment that is rich (85) sounds and sights.Also, the child should (86) hear the speech of other people.
A、unlessB、until
C、lest D、after