A、Turning on the TV. B、someone walking around the table. C、Improper question-asking. D、Disagreement between family members. A

　　As any homemaker who has tried to keep order at the dinner table knows, there is far more to a family meal than food. (22) Sociologist Michael Lewis has been studying 50 families to find out just how much more. Lewis and his coworkers carried out their study by videotaping the families while they ate ordinary meals in their own homes. They found that parents with small families talked actively with each other and their children. (23) But as the number of
　　children got larger, conversation gave way to the parents’ efforts to control the loud noise they made. That can have an important effect on the children. "In general, the more question-asking the parents do, the higher the children’s IQ scores are, " Lewis says, "and the more children there are, the less question-asking there is." (24) The study also provides an explanation for why middle children often seem to have a harder time in life than their brothers and sisters. Lewis finds that in families with three or four children, dinner conversation is likely to center on the oldest child, who has the most to talk about, and the youngest, who needs the most attention. (24) "Middle children are invisible," says Lewis. "When you see someone get up from the table and walk around during dinner, it’s often the case that it’s the middle child." There is, however, (25) one thing that stops all conversation and prevents anyone from having attention. "When the TV is on," Lewis says, "dinner is a non-event."
　　22.  What is the purpose of the passage?
　　23.  Why do parents with larger families ask fewer questions at dinner?
　　24.  Which statement would the speaker probably agree with?
　　25.  What will prevent all conversation at dinner?