What caused Columbia disaster according to this passage

A．The location of the computer.
B．The address of the website.
C．The new schedule.
D．How to find a new home.

A．They noticed an apparent change in the position of the North Star.
B．They observed eclipses at different times of the year.
C．They were the first to estimate the distance between heavenly bodies.
D．They wanted to prove that the Earth was fiat.