Answer:
C. how ignoring people is rude.
Step-by-step explanation:
The second paragraph discusses how cell phone usage can be disrespectful when there are other people around who can hear the conversation. It mentions that having a conversation on the phone when physically with another person can make that person feel ignored and unimportant. This suggests that ignoring people in favor of focusing on a cell phone can be rude or impolite behavior. Therefore, adding the information "how ignoring people is rude" would provide a complete summary of this aspect of the second paragraph.