Which of the following statements arecorrect?

You want to create a maintenance order with an external order operation with service items .

Which of the following statements arecorrect? Note: There are 3 correct answers to this question.
A . The usage of a model service specification is mandatory.
B. The assignment of a control key with the service indicator set is mandatory.
C. The actual value entry can only be recorded via the service entrysheet.
D. The assignment ofservice master records to an order operation is optional.
E. The assignment of a control key with the service indicator set is mandatory.

Answer: B,C,E