What caused Columbia disaster according to this passage

A．To introduce the woman to someone who has researched blushing.
B．To illustrate the benefits of a public-speaking class.
C．To give an example of someone who blushes easily.
D．To example a way to overcome blushing.

A．A place for making astronomical observations.
B．An instrument used for observing stars.
C．A trait of measurement.
D．The North Star.