Q-A (Senior citizens can) enjoy mountain walking (without) necessary skills. (On the other hand, their safety) cannot be guaranteed when there is anything unexpected in the mountains.
Q-B (People’s health) can be improved both physically and mentally.
(Mountainous regions) can gain considerable economic benefits from tourism.
Q-C In my opinion, people climbing in the mountains as a pastime should pay the full costs when they are rescued. First, such spare-time activities must be done at your own risk. These activities are not done to live, but to lead a more enjoyable life. Naturally, with them comes responsibility. Second, it is absurd to take a high risk to keep fit or make money. Mountain walking may be healthy and profitable, but it also involves the risk of losing your life. There are other safer alternatives to choose from to help you stay healthy or make a living. (99 words)