I believe that the option of "For middle-class families today, it usually takes two incomes to get by,..." because that does not specifically apply to only the women in the family, but that the male (or anyone else) is responsible for making up the other half of the income to pay for basic necessities.
When you think about words such as summer and friendship, usually you would have positive emotions relating to those words. Summer is the time when there's no school, and when you can spend a lot of time with your friends, which makes you happy. Thus, those words will create B. a positive mood.
