Please answer the following question: I want to test the ability of students to read a passage and answer questions about it. Could you please come up with a good question for the passage "Though Jehovah's Witnesses do not accept blood transfusions of whole blood, they may accept some blood plasma fractions at their own discretion. The Watch Tower Society provides pre-formatted durable power of attorney documents prohibiting major blood components, in which members can specify which allowable fractions and treatments they will personally accept. Jehovah's Witnesses have established Hospital Liaison Committees as a cooperative arrangement between individual Jehovah's Witnesses and medical professionals and hospitals."?
A:
What is the medical procedure that is prohibited for Jehovah's Witnesses?