TOEFL Listening: ETS-TOEFL听力机经 - S218HCLT3Z5FFHZCP$

Why did the researchers change the appearance and movement of the climber block in the second experiment? A. To make the climber block more visible B. To convey that the climber block was not alive C. To make the climber block more attractive to the infants D. To make the climber block appear more independent