Part A: The statement that best states a central idea of this text is the second option: "When helping others, it is important to act; words alone are not enough."
The first option ("Good people volunteer...") is incorrect because the text makes no generalizations about good people at all; the third option ("In times of crisis...") is incorrect because the interaction between older and younger people in the text is not relevant; the fourth option ("Most people...") is incorrect because the person who needs help in the text is not a stranger, but a friend.
Part B: The essential detail from the text that helps to shape the central idea in Part A is the fact that, despite receiving over fifty messages in social networks offering support (words), Martin and his father were actually only visited by Jerome that day (actions).