Run Time Error Encountered

[ddspell]

37. Which of the following requires a custom CloudWatch metric to
    monitoring?

A. Disk usage activity of the ephemeral volumes of an Amazon EC2
instance
B. CPU Utilisation of an Amazon Elastic compute cloud(EC2) instance
C. Disk usage activity of an elastic block store volume attached to an
Amazon EC2 instance
D. Disk full percentage of an Elastic Block store volume

C
Traceback (most recent call last):
File "C:\Users\Danny\Desktop\aws-flash-master\exam.py", line 82, in
run()
File "C:\Users\Danny\Desktop\aws-flash-master\exam.py", line 69, in run
correct_answers+= " : "+question['options'][correct_answer]
KeyError: 'd'