Fundamentally, an economic problem is a problem of---------------------
(Fill up the blank with correct alternative)
(a) Inaction (b) Lack of judgement
(c ) Choice (d) None of the above.

Dear Student,
Fundamentally, an economic problem is a problem of Choice, because Resources are in scarcity and how best to produce and distribute these scare resources. 
Therefore Option C is the correct answer.
Regards