One is that public transit does do a great deal to really make the urban______.

A．To see what would happen if the plane exploded in the water.
B．To see how much air passengers need to breathe at certain altitudes.
C．To find out if there are any weak parts that would burst under pressure.
D．To find out how much air can be pumped into a plane.

A．They make decisions by tossing coins.
B．They are not physically separated.
C．They think exactly the same way.
D．They share most of their vital organs.