The answer to this question would be: c.intrinsic motivation
Intrinsic motivation is a motivation to do something that comes from yourself. The example to this would be if you play games because it is fun. Extrinsic motivation would come from outside. The example would be if you working because someone gives you money for doing it.
In this case, the imaginary friend is created by the person himself so it is counted as intrinsic motivation, not extrinsic.
