How many astronauts died in the Columbia incident

A．Discover
B．Atlanta
C．Columbia
D．Atlantis

A．That it can't be measured.
B．That it doesn't change.
C．That it's getting smaller.
D．That it's rapidly increasin

A．Being too prudent and cautious.
B．Being too hasty to assure safety.
C．Causing the Columbia tragedy.
D．Delaying launch plans.