Final answer:
Both Technician A and B are correct with slight clarification for Technician A; valve seals are designed to prevent oil from leaking into the combustion chamber, and valve retainers are indeed used to hold the valve in the spring.
Step-by-step explanation:
The question is asking about the functions of valve seals and valve retainers in an internal combustion engine. Technician A states that valve seals are designed to prevent combustion gases from entering the valve train area. This is correct as valve seals are placed on the valve stem to prevent oil from the cylinder head from leaking into the combustion chamber. However, they are not primarily for preventing combustion gases from entering the valve train area; rather, they prevent oil from entering the combustion chamber.
Technician B says that valve retainers hold the valve in the spring. This statement is correct; valve retainers, in conjunction with keepers (or locks), are crucial components that fit on the top of the valve and connect it to the valve spring, keeping everything assembled and operational. Therefore, the correct answer is C. Both A and B.