The correct option is A. A directory of relatives' phone numbers
Explanation:
Family communication plan is a measure taken to contact the relatives of a person if an emergency situation arises for a person. In today's modern world, emergencies can happen at any time so it is very important to have a family communication plan so that the relatives of a person be informed immediately. Hence, option A is correct.
Other options are false because none of the other options will be usable in case of an emergency.
