Which actions apply to contract negotiations in SAP Ariba?

SAP Ariba Contracts Configuration

Which actions apply to contract negotiations in SAP Ariba? Note: There are 2 correct answers to this question
A . The project owner can launch only one round of a negotiation task
B. The supplier can modify a received contract document
C. The project owner cannot add observers to a negotiation task
D. The initial message must be entered before sending the task

Answer: B,D