Under Which Conditions Would You Expect a 9-Month-Old Baby to Make

Under which conditions would you expect a 9-month-old baby to make the strongest protest over separation?

A) The mother leaves the baby in a laboratory room and closes the door behind her.
B) The mother leaves the baby's sight but calls out to the baby from another room.
C) The mother leaves the living room and walks into the kitchen while the baby stays in the living room.
D) The mother walks from one laboratory room to an adjoining room while the baby watches.