DrFrankl Wants to Investigate Infant Language Learning

Multiple Choice

Dr.Frankl wants to investigate infant language learning.He wants to use parents' observations,but considers them biased and unreliable.How can he make the parents' observations more reliable and less biased using a single,inexpensive method?

A) Use computer simulations of the observations.
B) Use high-quality audio recordings of all parent-child interactions.
C) Use high-quality video recordings of all parent-child interactions.
D) Give the parents printed checklists for recording their observations.