What is the difference between intrinsic and extrinsic reinforcement?

a) Intrinsic reinforcement comes from within oneself, while extrinsic reinforcement comes from external sources
b) Intrinsic reinforcement is more effective than extrinsic reinforcement
c) Intrinsic reinforcement is always positive, while extrinsic reinforcement can be positive or negative
d) Intrinsic reinforcement is based on physical rewards, while extrinsic reinforcement is based on emotional rewards