You chose Choice Three, which is what actually happened. Challenging ideas about who should be in the operating room, Blalock asked Thomas to join him.
"When all was ready, Dr. Blalock asked me to stand where I could see what he was doing. The best vantage point was on a step stool placed so that I could look over his right shoulder. I watched closely as each suture was being placed. In such small vessels, it was necessary to place each stitch less than one millimeter from the last and very close to the edge of the vessel... On occasion, [Dr. Blalock] would ask if I thought a particular suture was being placed near enough to the preceding one. If he placed a suture in the wrong direction (which he did on several occasions, having better exposure in one direction than the other), I would say, the other direction."
-- Vivien Thomas, in his autobiography
Blalock has very little experience with the operation he is about to perform. While Thomas is unqualified to operate on a human child, Blalock will need his assistance to be successful.
As chief of surgery, Blalock is unafraid of flouting convention in pursuit of his medical goals, and he has little time for administrative niceties.
He has known and worked closely with Thomas for 15 years and has come to trust his judgment.
Blalock risks challenging the hospital administration over the presence of a technician in the operating room.
Fellow doctors and residents may question Blalock's ability to conduct the surgery on his own.
Although Thomas has performed the surgery in lab animals dozens of times, there is no guarantee that this skill will transfer to a surgery on a baby human.