Why is the fed often referred to as a ""lender of last resort

Read the following passage: sari couldn't believe her bad luck. she had locked her keys in the car. to add fuel to the fire, her cell phone was in the locked car, and she was late for a very important meeting. she knocked on her neighbor's door so that she could ask to use his phone, but he was not not home. what was she to do? what role does the idiom in the passage serve? a. it shows that sari has incredibly bad luck when it comes to work. b. it shows that sari's neighbor was not home either. c. it shows that sari locked her keys in the car. d. it shows that sari's situation was worse than it seemed at first.