Answer: The right answer is the D. It shows that Sari's situation was worse than it seemed at first.
Explanation: Just to elaborate a little on the answer, it can be added that the idiom "add fuel to the fire" has been used to indicate that a situation that was already bad (Sari had locked her keys in the car) got even worse (her cell phone was in the car, she had a meeting that day, and she could not use her neighbor's phone since he was not at home). Adding fuel to a fire literally makes the fire more intense, so by using this idiom figuratively here the author has tried to suggest that Sari's difficult situation only got worse by the subsequent challenges that she had to face that day.