A．Give an example.
B．For comparison.
C．It shows that teachers’ evolutions depend on the results of examinations.
D．It shows the results of court are more effective.

A．Molecules of interstellar formaldehyde can evolve into complex organic molecules.
B．Interstellar formaldehyde can be synthesized by tunneling.
C．Cosmic rays can directly synthesize complex organic molecules.
D．The galactic clouds are the places where prebiological evolution of compounds necessary to life occurred.