Limited __________ of resources and their limited potential is everybody's __________.
Step 1: The sentence speaks about scarcity of resources and the resulting responsibility.
Step 2: Among the options:
- (a) "assess, responsibility" → grammatically wrong.
- (b) "reach, game" → meaningless.
- (c) availability, concern → correct, as limited availability of resources is a matter of concern for all.
- (d) "area, knowledge" → contextually irrelevant.
Step 3: Thus, the correct choice is option (c). \[ \boxed{\text{availability, concern}} \]