The valve seat performs two functions: it provides a seal for the valve in the combustion chamber, and it provides a cool surface to carry heat away from the valve. most valves use a seating angle.

the answer to the question is punishment. or more specifically, positive punishment.

positive punishment occurs when a behavior is given a negative consequence for the individual doing the behavior.

sara no longer wants to ask questions (the behavior) because she is ridiculed by mr. smith (the punishment).

reinforcement is inaccurate because reinforcement always gives positive consequences for the individual doing the behavior, be it by introducing a pleasant consequence or removing an unpleasant one.

personal injury protection coverage covers your lost income if you are injured in a collision and also includes medical expenses regardless of who's at fault

i would imagine your answer to be b.

i'm not could be wrong.

(also for future reference, their is an 'arts' category. : )