What is the reason for the error message?

The probability technical success filed is enabled for questionnaires. You have defined a questionnaire for portfolio items In customizing. When you want to fill out the questionnaire for the probability technical success filed an error message is displayed.

What is the reason for the error message?
A . The field service configuration of the item is missing
B . The master switch for the interface settings for questionnaires it turned off
C . The probability technical success field is configured as read only in the field control
D . The field service configuration of the parent bucket of the item is missing

Answer: D