How many adults were killed in the explosion

A．Children playing with fire.
B．The setting off of fireworks in a house with explosives,
C．Sparks from a fireworks display falling on the warehouse,
D．The firing of a gun.

A．they lost a little ability to reason over the years
B．the only factor which declined over the years was their speed with which to perform mental tasks
C．their memory was not as good as it had once been
D．their minds became a bit more active as they grew older