When should you open a credit card account?
when you want to take an exotic vacation
when you have a plan for paying it back
when you need new clothes for an event
when you want to loan money to a friend

2. when you have a plan for paying it back

Explanation:

You have to pay back the money you use from the card. Thus, its the only answer that makes sense.

the assumption the narrator makes in this excerpt is that the messages he heards were going to hurt the narrator's mom; the narrator just springs in to action. the narrator doesn't specify in this excerpt why he believes that the messages present a problem that requires protection.