Read the passage and answer the questions about it below.

Question

A Study in Altruism
Whether it is the earthquake in Haiti, the tsunami in Indonesia, or the terrorist attack on the World Trade Center towers, as thousands of people flee for their lives, others rush in to rescue survivors. At the World Trade Center in 2001, for example, firefighters, emergency medical technicians, police officers, and civilians were the heroes of the tragedy. Theirs were acts of great altruism. They put their own survival at risk and sacrificed themselves to save others. We rightly honor anyone who displays such heroic altruism.
Surely some aspects of the ability to act in self-sacrificing ways on behalf of others are innate, but
just as surely, this behavior can be learned as well. In the case of firefighters, police officers, and others whose jobs require them to take risks to save others, much of what we understand as altruistic behavior is instilled during their rigorous training as recruits. A few weeks after the September 11 tragedy, the Fire Academy of New York City graduated 250 new firefighters. On the stage at the graduation ceremony were six empty chairs. Each was marked with an American flag or other symbol indicating that the seats were vacant because these probationary firefighters, or “probies” as they are called, were killed when the buildings collapsed. They were serving as trainees in firehouses that responded early to the alarms and thus had the greatest number of casualties. Like the more seasoned veterans who were killed in the collapse of the buildings, the probies were “just doing their jobs.”
Another aspect of what we see as altruism comes from the intense bond of friendship that is formed
by small groups who encounter highly dangerous situations. The self-sacrificing behavior that we
understand as altruism also stems from each individual’s belief that he or she must pitch in to help the group, not just to help strangers. The intensity of the peer bonds among firefighters, for example helps explain the intense feelings they displayed when asked to withdraw from the Ground Zero site. The firefighters regard the area as sacred ground and did not want to be excluded from the search for the bodies of their missing comrades.
The altruistic behavior of so many on that day also provided a model of altruism for a generation of
children throughout the world. The Halloween following the event saw a tremendous display of
firefighter, nurse, and police costumes as children embraced and emulated the behavior of their new
heroes.

Which of the following is the topic sentence of paragraph 3?
a. “Another aspect of what we see as altruism comes from the intense bond of friendship
that is formed by small groups who encounter highly dangerous situations.”
b. “The self-sacrificing behavior that we understand as altruism also stems from each
individual’s belief that he or she must pitch in to help the group, not just to help
strangers.”
c. “The intensity of the peer bonds among firefighters, for example helps explain the
intense feelings they displayed when asked to withdraw from the Ground Zero site.”
d. “The firefighters regard the area as sacred ground and did not want to be excluded from
the search for the bodies of their missing comrades.”

Answer 1

b. “The self-sacrificing behavior that we understand as altruism also stems from each
individual’s belief that he or she must pitch in to help the group, not just to help
strangers.”