What Type of Procedure Is Appropriate to Isolate Revertants from a Population

Multiple Choice

What type of procedure is appropriate to isolate revertants from a population of threonine auxotrophic cells?

A) Grow the auxotrophic cells on an agar plate without threonine; any colonies that form are presumed revertant.
B) Grow the auxotrophic cells on and agar plate with threonine; any colonies that form are presumed revertant.
C) Grow the auxotrophic cells in broth with threonine; if the broth becomes cloudy,revertants are presumed present.
D) Threonine auxotrophic revertants could not be isolated on any type of media.