TOEFL Reading: ETS-TOEFL阅读机经 - 92IEOXE5J_J9Y41AL$

Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information. A. Infants of about a year old begin using their index finger and thumb to make more coordinated and finely tuned movements, allowing them to explore and manipulate small objects. B. Around the end of the first year, infants begin to use a type of grip on small objects that is more coordinated and finely tuned than was the pincer grasp. C. Infants begin handling very small or difficult-to-operate objects at about one year of age, resulting in improvements in their ability to grip objects with their thumb and fingers. D. When one-year-old infants begin using the pincer grasp, they become much more interested in very small objects (such as knobs on a stereo system).