Which of the Following Could Be Considered an Inappropriate Interview

Which of the following could be considered an inappropriate interview question?

A) Tell me your family situation. Who will take care of the children when they are home sick from school?
B) Tell me about a time when you tried to do something and you were not successful. How did you handle that?
C) Tell me about a time you had to deal with a difficult customer. What happened?
D) Tell me about a time when you had to make a difficult decision on the job. What did you do?