In a Story Reported in the Text, a Group of Researchers

In a story reported in the text, a group of researchers observed that newborn boys cried more often than newborn girls for no apparent reason. The researchers did not think about the fact that the boys had recently been circumcised. What does this story demonstrate about the nature of observation?

A) During observation, the observer may have different reactions to different children.
B) Observation is difficult without having dual focus skills.
C) Adults can sometimes learn as much about themselves as they do about the children during observations.
D) Observation is not easy; sometimes even skilled observers miss the obvious.